1985 with an Expanded Story on Electronics in Photography That Everyone Should Read

of Electronics News and Tips RdìO._ 134 that'llpages change your every -day life Electronucsi co

$2.50-US/$2.05-CANADA Home ELECTRONICS in Control PHOTOGRAPHY Computer

NIKOLA TESLA CABLE -TV DESCRAMBLING how to Design

GERNSBACK DC POWER SUPPLIES PUBLICATION Exhaust Analyzer for your car [)

C-DUAM Stereo-AM o Decoder ii TEK Now! Tek quality and expert advice are just a free phone call away!

100 MHz dual A/B sweep selec- time base scope. tion. Calibrated Easy -to -read CRT; Wide range verti- A sweeps from bright, full-sized cal sensitivity. Two 100 MHz, 50 ns/div to 8x10 cm; 14 kv Choose from high sensitivity 0.5 s/div; B sweeps accelerating 2 mV/div (lx channels. 3.5 ns from 50 ns/div B trigger slope potential complete probe) to 50 V/div risetime; do to to 50 ms/div; vari- and level. Use B with BEAM FIND, (10x probe); 100 MHz band- able control for up Dual time base trigger level to separate NB color -keyed for lx width from 5 V/div to 2.5 to 1 reduc- measurements. select B -triggered dual intensity and 10x probes; to 5 mV/div; tion and 10x Select either A or or run -after -delay controls, FOCUS variable control extended sen- magnification for B sweeps, or both modes; use B and TRACE increases scale sitivity of 2 mV/div sweeps to alternately with A TRIGGER SLOPE ROTATION. factor by 2.5 to 1. at 90 MHz. 5 ns/div. intensified by B. to select transitions.

Our direct order line gets have the bandwidth for digital you the industry's leading and analog circuits. The sensitivity price/performance portables... for low signal measurements. The and fast answers from experts! sweep speeds for fast logic fami- manual, two 10X probes, 15 -day The 60 MHz single time base delay lies. And delayed sweep for fast, return policy and worldwide ser- 2213A, the 60 MHz dual time base accurate timing measurements. vice backup. 2215A and the 100 MHz dual time All scopes are UL Listed and CSA base 2235 offer unprecedented approved. Order toll free: reliability and affordability, plus the You can order, or obtain 1-800-426-2200, industry's first 3 -year warranty* literature, through the Tek on labor and parts, CRT included. National Marketing Center. Tech- Ask for Rick. In Oregon, call collect: The cost: just $1200 for the nical personnel, expert in scope 2213A, $1450 for the 2215A, applications, will answer your (503) 627-9000. $1650 for the 2235.1 Even at questions and expedite delivery. Or write Tektronix, Inc. these low prices, there's no Direct orders include comprehen- P.O. Box 1700 scrimping on performance. You sive 3 -year warranty*, operator's Beaverton, OR 97075

Tektronix COMMITTED TO EXCELLENCE

A Picture is Worth a Thousand Words!

I I can remember the day when bracketed my photographic shots, plus and minus half -stops, to be sure that at least one of the negatives obtained would be good enough for making a black -and -white 5 x 7 print. Now I shoot with abandon! My camera measures the light, automatically selects the correct focus, fires the strobe, makes an exposure, and the results are fantastic full -color snaps available that same day. Electronics made it all possible. We can't cover all the electronics advancements in photography in one issue of a magazine, let alone in one issue of a thick book; but we open this issue of the Radio - Electronics Annual 1985 with an expanded story on electronics in photography that everyone should read. In fact, if you are a nostalgia buff, save this issue-we predict that ten years from today what we say here will be old hat as is the brownie camera of Grandma's day. Our cover displays three construction projects that, quite frankly, we hope will bring excitement to you as they did to us. CIRCLE 267 ON FREE INFORMATION CARD In fact, check out the contents page and discover a few other Radio - interesting project articles. We included a few macro projects Electronics that we know will get you thinking about designing your own projects Of course, the issue is packed with many other features- UAL the life and times of Nikola Tesla, cable -TV descrambling, STAFF designing power supplies, unique test equipment, inside logic Hugo Gernsback (1884-1967) founder in, and enjoy this issue analyzers, and a lot more. Dig friends, M. Harvey Gernsback, editor-in -chief of Radio -Electronics Annual 1985. Larry Steckler, CET, publisher

Art Kleiman, editorial director

Julian S. Martin, KA2GUN, editor

Af. ,1,,c,,704'.. Carl Laron, associate editor

Brian C. Fenton, assistant technical editor (244w.1Julian S. Martin, KA2GUN Ruby M. Yee, Editor production manager Robert A.W. Lowndes, production associate BUSINESS AND EDITORIAL OFFICES PACIFIC COAST Mountain States Karen S. Tucker, production associate Gernsback Publications, Inc. 200 Park Ave. South, New York, NY 10003 Marvin Green Dianne Osias, President: M. Harvey Gernsback Radio -Electronics production assistant Vice President: Larry Steckler 413 So. La Brea Ave. Los Angeles, Ca. 90036 Jacqueline Weaver, circulation director (213) 938-0166 Arline R. Fishman, ADVERTISING SALES MIDWEST/Texas/ advertising coordinator East Arkansas/Okla. Composition and interior design by Stanley Levitan Ralph Bergen Mates Graphics Radio -Electronics The Ralph Bergen Co. 200 Park Ave. South 540 Frontage Road-Suite 325 C) Y New York, NY 10003 Northfield, Illinois 60093 212-777-6400 312-446-1444

1 - Rádió Electróñçs) 1985

CONTENTS PAGE

21 ELECTRONICS IN PHOTOGRAPHY-all areas of photography have benefitted from the use of electronics in photographic equipment 21-Introduction 23-The All -Electronic Mavica 27-The New Disc Cameras 31-Auto Exposure and Auto Focus Systems 38-Photo Accessories 42-Electronics in the Darkroom

46 Audio Frequency Generator-designed with a quick -reading, digital readout

51 The Life and Times Of Nikola Tesla-he made possible much of what we take for granted today 59 C-QUAM AM Stereo Converter-one chip brings stereo to your AM receiver 65 Unique Test Equipment-a look at what's new, what's sophisticated, and what's unusual 71 Solid -State Barometer-state-of-the-art device you can build

75 How to Design Power Supplies-all about unregulated and regulated power supplies, and overvoltage protection circuits 79 Home Control Computer-it can do the job and free your home computer for other purposes 94 TRS-80 Telephone Dialer-go automatic with this program 95 Automotive Exhaust Analyzer-lets you tune up for emission requirements

107 Cable TV Descrambling-how they do it and undo it 111 Making Measurements Electronically-how transducers make it all possible 116 Upgrade Your Printer-add new features and flexibility 121 All About Logic Analyzers-the digital equivalent to the oscilloscope MACRO PROJECTS 106 Sliding -Tone Doorbell 106 Plant -Water Monitor 130 Crystal Tester DEPARTMENTS

1 Editorial-one picture is worth a thousand words! 4 New Products-hot items in the marketplace 14 Equipment Reports 14-Ungar Electronic Soldering Iron System 9000 14-Regency Programmable Scanner Model Z30 127-Triplett Model 3500 Autorange Digital Meter 128-Beta Electronics Pro -Kit 1 PC Board Fabrication Kit 129-Kaypro 10 Hard -Disk Computer

Radio -Electronics Annual is published yearly by Gernsback Publications, Inc., 200 Park Avenue South, New York, NY 10003. Single copies $2.50 plus $1.00 postage and handling for U.S., Canada and Mexico. U.S. funds only. All other countries add $2.00. C 1984 by Gernsback Publications, Inc. All rights reserved. Printed in U.S.A.

As a service to readers, Radio -Electronics Annual publishes available plans or information relating to newsworthy products. techniques and scientific and technological developments. Because of possible variances in the quality and condition of materials and workmanship used by readers, Radio -Electronics Annual disclaims any responsibility for the safe and proper functioning of reader -built projects based upon or from plans or information published in this magazine.

2 Take home a world champion.

S gets you a technical knockout. 85* The Fluke 70 Series. Winners of the digital vs. analog battle. Since their debut, they've become the worldwide champions of the industry. Never before have such tough, American - made meters offered so many professional features at such unbeatable prices. Each comes with a 3 -year warranty, 2,000+ hour battery life, and instant autoranging. You also get the extra resolution of a 3200 - count LCD display, plus a responsive analog bar graph for quick visual checks of continuity, peaking, nulling and trends. Choose from the Fluke 73, the ultimate in simplicity. The feature -packed Fluke 75. Or the deluxe Fluke 77, with its own protective holster and unique "Touch Hold" function** that captures and holds readings, then beeps to alert you. So don't settle for just a contender. Take home a world champion. For your nearest distributor or a free brochure, call toll -free anytime 1-800-227-3800, Ext. 229. From outside the U.S., call 1-402-496-1350, Ext. 229. FROM THE WORLD LEADER IN DIGITAL MULTIMETERS.

FLUKE 73 FLUKE 75 FLUKE $85* $99' $129* Analog/digital display Analog/digital display Analog/digital display

Volts, ohms, 10A, diode Volts, ohms, 10A, mA, Volts, ohms, 10A, mA test diode test diode test Autorange Audible continuity Audible continuity 0.7% basic dc accuracy Autorange/range hold "Touch Hold" function 2000+ hour battery life 0.5% basic dc accuracy Autorange/range hold 3-year warranty 2000+ hour battery life 0.3% basic dc accuracy 3 -year warranty 2000+ hour battery life 3 -year warranty Multipurpose holster

Suggested U.S. list price, effective July 1, 1984. ** Patent pending. FLUKE

DIGITAL PANEL METER, the model automatic polarity indication for The 0.563 -inch LED readout, X-34 Thriftmeter, is an LED -readout positive and negative input volt- with programmable decimal digital panel meter with a 0.5 -inch ages, out -of -range overload in- point, is readable from 30 feet. The depth behind the case. The 31/2 - dication, and accuracy to 0.001 meter is designed for scientific digit, 2000 -count meter features volt. analytical equipment, medical equipment, and test and process -

VIEW 8 TRACES ON YOUR SINGLE OR DUAL TRACE SCOPE WITH THIS LOW COST DEVICE!!

Now you no longer have to spend thousands on an expensive multi - CIRCLE 231 ON FREE INFORMATION CARD trace oscilloscope - our single trace Hitachi scope combined with this module will allow you to view up to 8 control equipment, as well as ap- 1-4 5-8 I-8 simultaneously occuring analog or MI digital (or both) signals in their real plications for hobbyists and elec- sMt time and amplitude relationship. The E W fI.GAJEfAYK AC MPX 101 may be used on any oscil- tronics experimenters. Calcula- loscope, whether single, dual or mul- M1AX MIN MAX tiple traces. Its low cost makes it a tions involving meter loading are AMPLITUDE SPACING CNANNEL particular favorite for designers, test- NM SELECT ers, hobbyists and repairmen who eliminated, in most cases, by the POWER OUTPUT want to compare and analyze dis- high -impedance input. HI 1.0 played signals in a timing diagram INPUT format. The controls on the front The model X-34 Thriftmeter SAMPLE RATE panel of the metal case allow you to vary amplitude and spacing of the comes with a case, red readout - displayed signals. filter, and mounting hardware, and MODEL MPX101 is priced at $38.50.-Non-Linear FULLY ASSEMBLED & TESTED! Systems, 533 Stevens Avenue, So- lana Beach, CA 92075.

88 TEST LINE SIMULATOR, model FULL 1 YEAR TLS -2, is designed to provide a REPLACE- MENT telephone/telephone system in- WARRANTY staller a means to perform opera- - Made In The United States - tional and functional checks of SPECIFICATIONS telephone and system installations Inputs: 8 signals plus ground via 9 150 mV/step @ 5V Input input leads terminated with alliga- Multiplex Rate: Switch selectable, 40 when central -office lines are not tor clips KHz or 4 KHz available. Bandwidth: ± 1dB to 5 MHz Impedance: 50 Ohms Impedance: 10.9 K Power: 105-135 VAC @ 1 V a The model TLS -2 includes the Input Voltage: ± 5V peak (diode Dimensions: 6.25" x 3.25" x clamped to ± 5 Volt supplies) 4.75" (WxHxD) following features: It provides Output: Staircase waveform summed Operating Temperature: 0-40°C loop and ground -start operation; with input signals, 0-800 mV Weight: 1 lb. 10.5 oz. full scale Warranty: one year full replacement two lines are provided with sepa - Step Amplitude: Variable 0 to 150 warranty from date of purchase mV/ step Lighted on/off power switch Signal Voltage: Variable 0 to Wood grain finished metal case DISTRIBUTOR AND REPRESENTATIVE INQUIRIES INVITED ,--iv,IR E.W. ENGINEERING, INC VISA, MASTERCARD, AMEX TELEPHONE ORDERS ACCEPTED! 6 Herman Drive, E. Granby, CT 06026 I=1203/651-0285 CIRCLE 232 ON FREE INFORMATION CARD CIRCLE 214 4 ON FREE INFORMATION CARD PARTIAL LISTING ONLY - PLEASE CALL OR WRITE FOR FREE CATALOG. r r 6500 74LS00 STATIC RAMS r 8000 6502 4.95 rCRYSTALS, r 8039 5.95 74LSOO .24 74LS157 .65 2114 1024 x 4 (450ns) 819.95 6.95 32.768 khz 1.95 8080 3.95 6522 74LS02 .25 74LS158 .59 2114-25 1024 x 4 (250ns) 8110.95 6502A 6.95 8085 4.95 74LS03 .25 74LS161 .65 2114L-2 1024 x 4 (200ns) (LP) 8113.95 1.8432 3.95 8087 175.00 74LSO4 .24 74LS163 .85 TMM2016-200 2048 x 8 (2COns) 4.15 6800 2.0 2.95 8088 29.95 74LS05 .25 74LS164 .69 TMM2016-150 2048 x 8 (15Ons) 4.95 6802 7.95 2.4576 2.95 8155 6.95 741S08 .28 74LS165 .95 TMM2016-100 2048 x 8 (1COns) 6.15 6809E 14.95 8748 24.95 3.276 2.95 74LS09 .29 74LS169 1.75 HM6116-4 2048 x 8 (2COns) (cmos) 4.75 6821 2.95 3.579545 2.95 74LS11 .35 74LS173 .69 HM6116.3 2048 x 8 (15Ons) (cmos) 4.95 6845 14.95 8200 4.0 2.95 74LS14 .59 74LS174 .55 HM6116LP-4 2048 x 8 (200ns) (cmos) (LP) 5.95 8203 39.95 6850 3.25 5.0 2.95 74LS20 .25 74LS191 .89 HM6116LP3 2048 x 8 (15Ons) (cmos) ;LP) 6.95 8205 3.50 6883 22.95 5.0688 2.95 74LS21 .29 74LS193 .79 HM6264 8192 x 8 (15Ons) (cmos) 39.95 8212 1.80 DISK 1.75 CONTR 6.0 2.95 74LS27 .29 74LS194 .69 LP = Low Power 8216 1771 24.95 3.49 6.144 2.95 74LS30 .25 74LS195 .69 8228 1791 24.95 82375 21.95 8.0 2.95 74LS32 .29 74LS221 .89 DYNAMIC RAMS 1793 26.95 74LS33 .55 74LS240 .95 4116-250 16384 x 1 (250ns) 817.95 8243 4.45 10.0 2.95 2791 54.95 74LS38 .35 74LS241 .99 4116.200 16384 x 1 (200ns) 8112.95 8250 10.95 10.738635 2.95 2793 54.95 74LS42 .49 74LS242 .99 4116.150 16384 x 1 (15Ons) 8114.95 8251 4.49 14.31818 2.95 74LS47 .75 74LS243 .99 4164.200 65536 x 1 (200ns) (5v) 9149.00 8253 6.95 15.0 2.95 INTERFACE 74LS51 .25 74LS244 1.29 4164-150 65536 x 1 (15Ons) (5v) 9149.00 82535 7.95 8728 1.89 16.0 2.95 74LS73 .39 74LS251 .59 TMS 4164.15 65536 x 1 (15Ons) (5v) 8.95 8255 4.49 8797 .89 17.430 2.95 74LS74 .35 74LS257 .59 8255.5 5.25 DM8131 2.95 5v = Single 5 roll supply L20.0 2.92 74LS75 .39 74LS258 .59 8259 6.90 DP8304 2.29 74LS76 .39 74LS259 2.75 8259-5 7.50 9334 2.50 EPROMS 74LS85 .69 74LS260 .59 2708 1024 x 8 (450ns) 3.95 8275 29.95 9368 3.95 74LS86 .39 74LS266 .55 2716 2048 x 8 (450ns) (5v) 3.95 8279 8.95 DISCRETE1 74LS90 .55 74LS273 1.49 2716.1 2048 x 8 (350ns) (5v) 5.95 8282 6.50 CLOCK CHIPS KBP02 Bridge .45 74LS92 .55 74LS279 .49 TMS2532 4096 x 3 (450ns) (5v) 5.95 8284 5.50 MM5369 3.95 1N751 5.1v zener .25 74LS93 .55 74LS280 1.98 2732 4096 x d (450ns) (5v) 4.95 8286 6.50 MM58167 12.95 1N759 12v zener .25 74LS107 .39 74LS283 .89 2732.250 4096 x 3 (250ns) (5v) 8.95 MSM5832 3.95 2N2222 .25 74LS109 .39 74LS290 .89 2732-200 4096 x 3 (200ns) (5v) 11.95 Z-80 PN2222 .10 DATA ACQ 74LS112 .39 74LS293 .89 2732A 4096 x 3 (250ns) (5v) (21vPGM) 9.95 Z80 -CPU 3.95 2N2905 .50 ADC0804 3.49 74LS122 .45 74LS299 1.75 2732A-2 4096 x 8 (200ns) (5v) (21vPGM) 13.95 Z80PIO 3.95 2N2907 .25 ADC0809 4.49 74LS123 .79 74LS323 3.50' 27128 16384 x 8 (300ns) (5v) 29.95 Z80ACPU 4.49 12N3055 .79 Z80ACTC 4.95 ADC0817 9.95 74LS125 .49 74LS365 .49 5v = Single5voltsupply 21vPGM = Programat21 Volts 2N3904 .10 Z80APIO 4.49 SOUND CHIPS L2N3906 .10 74LS126 .49 74LS367 .45 Z80A-S1010 12.95 1N4004 1011.00 74LS132 .59 74LS368 .45 SPECTRONICS CORPORATION 76488 5.95 74LS133 `80B CPU 9.95 Y38910 12.95 1N4148 25/1.0 .59 74LS373 1.39 EPROM ERASER PE -14. 9chipcapacity 83.00) 74LS136 .39 74LS374 1.39 ( LA 74LS138 .55 74LS377 1.39 74LS139 .55 74LS390 1.19 74LS148 1.35 74LS393 1.19 4r IC rRESISTORS" SOCKETS" ORDER TOLL FREE r LINEAR 74LS151 .55 74LS640 2.20 1/4 WATT 5% CARBON 1-99 100 TL084 2.19 74LS153 .55 74LS670 1.49 FILM ALL STANDARD 8 pin ST .13 .11 LM301 .34 74LS154 1.90 74LS682 3.20 VALUES FROM 1 OHM 14 pin ST .15 .12 L M 307 .45 74LS156 .69 74LS688 2.40 TO 10 MEG OHM 16 pin ST .17 .13 LM 311 .64 18 .20 800-530-5000 pin ST .18 LM3177 1.19 20 pin ST .29 .27 LM319 1.25 74500 50 PCS./VALUE .025 22 pin ST .30 .27 74S00 .32 74S86 .50 100 PCS./VALUE .02 L M 324 .59 24 pin ST .30 .27 LM339 .99 74502 .35 74S112 .50 1000 PCS.NALUE .015 28 pin ST .40 .32 800-882-6279 74SO4 .35 74S124 2.75 LF351 .60 40 pin ST .49 .39 (CALIFORNIA RESIDENTS( 74S05 .35 74S138 .85 64 pin ST 4.25 call LM353 1.00 DIP LM358 .69 74S08 .35 74S157 .95. ST = SOLDERTAIL L M 380 .89 74S10 .35 74S175 .95 SWITCHES 8 pin WW .59 .49 LM386 .89 74S11 .35 74S240 2.20 14 pin WW .69 .52 4 POSITION .85 D -SUBMINIATURE CONNECTORS LM393 1.29 74S20 .35 74S280 1.95 16 pin WW .69 .58'. DBO9P Male 9 Pin D -Sub $2.08 74S32 .40 74S287 1.90 5 POSITION .90 18 .99 .90 TL497 3.25 pin WW DB25P Vale 25 Pin D -Sub 2.50 74S74 .50 74S288 1.90 6 POSITION .90 20 pin WW 1.09 .98 NE555 .34 DB25S 25 Pin D -Sub 3.25 7 POSITION .95 22 pin WW 1.39 1.28 remale NE558 1.50 DB25SR mamale 25 Pin Right Angle PC 4.42 8 POSITION .95 24 pin WW 1.49 1.35 N E564 2.95 7400 GREY HOOD for DB25 Connectors 1.25 28 pin WW 1.69 1.49 LM565 .99 7400 .19 7447 .69 MISC. 40 pin WW 1.99 1.80 IDC CONNECTORS L M 566 1.49 7402 .19 7473 .34 WW = WIREWRAP IDS26 26 Pin Ribbon Socket 2.43 LM567 .89 ULN2003 2.49 7404 .19 7474 .33 16 pin ZIF 6.95 call IDS34 34 Pin Ribbon Socket 3.15 NE592 2.75 3242 7.95 7405 .25 7475 .45 24 pin ZIF 7.95 call IDS50 50 Pin Ribbon Socket 4.65 LM723 .49 7406 .29 7476 MC3470 4.95 .35 28 pm ZIF 8.95 call IDE34 34 Pin Ribbon Edge Card 3.25 LM741 .35 7407 .29 7486 .35 AY5.1013 3.95 ZIF = TEXTOOL IDP16 16 Male Pin Dip Plug 1.65 LM 1303 1.95 7408 .24 7490 .35 iEOM8116 10.1 (Zero Insertion Force) 0050 50 Conductor Ribbon Cable 1.38/ft. MC1408L8 2.95 7410 .19 7492 .50 L M 1458 .59 7411 .25 7493 .35 LM1488 .69 7414 .49 74121 .29 LM 1489 .69 7416 25 74123 .49 JUMBO LEDS rCAPACITORS, XR2206 3.75 7417 .25 74132 .45 PERIPHERALS I.99 100 -up DISC XR2211 5.25 7420 .19 74151 .55 RED .10 .09 10pí S6pf CA3146 1.85 7425 .29 74154 1.25 LM3914 3.95 JDR HALF -HEIGHT DISK DRIVE GREEN .18 .15 22pf 82pí 7430 .19 74157 .55 27pí 100pí 75150 1.95 7432 *TEAC MECHANISM -DIRECT DRIVE YELLOW .18 .15 .29 74164 .85 33pí 220pí 75154 1.95 7438 .29 74168 1.00 100% APPLE COMPATIBLE TRACK -35 MOUNTING HARDWARE 47pí .001uí 75188 1.25 7442 .49 74192 .79 *40 TRACK WHEN USED WITH OPTIONAL 75189 1.25 .10 EA. 1001.09 EA. 50V, .054 EACH 7445 .69 74193 .79! CONTROLLER $11 78057 .75 MONOLITHIC 7808T .75 * 1 YEAR WARRANTY .14 6995 DISPLAYS .01uí -mono 50V 7812T .75 CMOS MAN 72 CA.3" .99 .047uí -mono 50V .15 781ST .75 4001 .25 4069 .29 50V .18 40 TRACK CONTROLLER 54995 MAN 74 CC.3" .99 tuf -mono 7805K 1.39 4011 .25 4070 .35 .47uf-mono 50V .25 FND-357 CC.375" 1.25 7812K 1.39 4013 .38 4071 .29 4015 .39 4081 FD -35 FULL HEIGHT DISK DRIVE FND-500 CC.5" 1.49 ELECTROLYTIC 78H05K 9.95 .29 RADIAL 78L05 .69 4016 .39 4093 .49 * MADE IN USA FND507 CA.5" 1.49 1uí 25V .14 78L12 .69 4017 .69 14411 11.95 SHUGART MECHANISM $17995 47uí 35V .18 79051 .85 4020 .75 4511 .85 * FULL 1 YEAR WARRANTY 470uí 25V .30 79127 .85 4024 .65 4518 .89 2200uf 16V .60 79L05 .79 4027 .45 4520 .79 CONTROLLER FOR FD -35 54995 r ELCOMP AXIAL 79L12 .79 4040 .75 4553 5.79 Handbook 50V .14 4042 .69 4584 .75 Hardware lut T = TO -220 K=10.3 22uí 16V .14 4046 .85 74C00 .35 Mfr's Specs: LOGIC, L = TO.92 BMX8080cps Bi.Directional $24900 47uf 50V .20 4049 .35 74C04 .35 MEMORY. MPU's & more 220uí 25V .30 4050 .35 74C74 .35 JDR 16K RAM Card $3995 HEAT SINKS COMPUTER GRADE TO -3 style 95 4051 .79 74C925 5.95 800 pas $1495 30V 3.95 L4066 .39 74C926 7.92 Power Supply 4amp Model $4985 L 44000u `0.220 style .32 VISIT OUR RETAIL STORE HOURS: M -W -F, 9-5 T -Th., 9-9 Sat. 10-3 PLEASE USE YOUR CUSTOMER NUMBER WHEN ORDERING JDR Microdevices TERMS: Minimum order $10. For shipping and handling include $2.50 for UPS Ground and $3.50 for UPS Air. Orders over 1 lb. and Mie1224 S. Bascom Avenue, San Jose, CA 95128 foreign orders may require additional shipping charges - please contact our sales department for the amount. CA residents must 800-538-5000 800-662-6279 (CA) include 6% sales taxi. Bay Area and LA residents include 61/2°t.?Prices subject to change without notice. We are not responsible for (408) 995-5430 Telex 171-110 typographical errors. We reserve the right to limit quantities and to All merchandise subject to prior sale. c Copyright 1984 JDR Microdevices APPLE IS A TRADEMARK OF APPLE COMPUTER CO. substitute manufacturer.

CIRCLE 211 ON FREE INFORMATION CARD

and wide and narrow audio -filters. NEW PRODUCTS It is available either as the standard continued from page 6 model 70x or the stereo version, model 70s, which decodes both rate battery feeds; it accepts tone matrix and discrete stereo sound. and rotary input; it has a unique The System 70x is priced at station number for each line; $750.00; the System 70s costs there is a ringing -voltage source $900.00. -Lowrance Electronics, with short-circuit protection, and Inc., 12000 E. Skelly Drive, Tulsa, there are three ways to apply ring- OK 74128. ing to on -hook lines. The TLS -2 sells for $290.00.--Teltone Corpora- INTERFACE, model 200-C488, is an tion, 10801 120th Avenue, NE, PO FREE IEEE -488 GPIB (General Purpose Box 657, Kirkland, WA 98033. CIRCLE 233 ON INFORMATION CARD Interface Bus) interface that HX-93 is priced at $1195.00.-Hol- provides talker -listener functions TEST SET, model HX-93, is de- lex, Inc., 81 W. Wyoming Avenue, for the full series of Bertan's ex- signed for testing installed cables. MA 02176. panded 205A/210 laboratory high - The unit features interchangeable voltage power supplies now avail- adapter plates for one cable end, SATELLITE RECEIVER, the System able. (Those supplies have output while the remote cable end con- 70, features detent tuning, polarity voltages to 75 kilovolts and output nects to a passive connector control, a signal -strength meter, power to 250 watts.) block. All lines are checked elec- built-in modulator, scan tuning, tronically for shorts and opens, as well as miswires. Testing can be initiated at either end; a PASS/FAIL indicator is included on the remote -connector block. Spring -loaded probes on the tester assure reliable connection to the adaptor plates. The model CIRCLE 234 ON FREE INFORMATION CARD

CIRCLE 235 ON FREE INFORMATION CARD Ial it Eleerr.ides BOOKSTORE Commands that are imple- Build Your Own Satellite TV Receiver $7.00 Special Projects (Spring 1981) $4.50 mented via the interface include 8 -Ball Satellite TV Antenna $5.00 Special Projects #4 (Summer 1982) $4.50 Build Your Own Robot Special output -voltage setting, voltage $12.00 _ Projects #5 (Winter 1983) $4.00 TV Descrambler (January, February 1981) $3.00 Special Projects #6 (Spring 1983) $4.00 limit, and current limit. In re- Radio -Electronics back issues (1984) $3.00 ú Special Projects #7 (Summer 83) NOT AVAILABLE sponse to a controller request, the Radio -Electronics back issues (1983) $3.50 Special Projects #8 (Fall 83) $4.00 Write in issues desired Special Projects #10 (Spring 84) $3.00 interface supplies power -supply E Radio -Electronics back issues (1982) $4.00 Radio -Electronics Annual 1983 $3.50 status and output data. It can be (January 1982 not available) Radio -Electronics Annual 1984 $2.50 programmed to automatically shut Write in issues desired E How to Make PC Boards $2.00 El Radio -Electronics back issues (1981) $4.00 All About Kits $2.00 down a power supply and request (Jan., Feb., March, Dec. 1981 not available) Modern Electronics (Vol. 1. #1 $2.25 service for an overvoltage or over - Write in issues desired April 1908) E Etch your own PC boards $3.00 Electro Importing Co. Catalog $4.95 current condition. (1918) (176 pp) The model 200-C488 interface is Low Frequency Receiving Techniques $6.00 To order any of the items indicated priced at $1,000.00.-Bertan Asso- above, check off the ones Building and using VLF Antennas you want. Complete the order form below, include your pay- ciates, Inc., 3 Aerial Way, Syosset, ment, check or money order (DO NOT SEND CASH), and mail NY 11791. to Radio -Electronics, Reprint Department, 200 Park Ave. ARTICLE South, New York, NY 10003. Please allow 4-6 weeks for continued on page 10 delivery MONTH YEAR If you need a copy of an article that is in an issue we indicate is unavailable you can order it directly from us. We charge 500 per page. Indicate the issue (month & year), pages and article PAGES

desired. Include payment in full, plus shipping and handling @ 500 each charge. TOTAL PAGES TOTAL PRICE

MAIL TO: Radio-Electronics AN5 Reprint Department, 200 Park Ave. South, New York, NY 10003 All payments must be in U.S. funds Total price of order S Sales Tax (New York State Residents drily) $ Shipping & Handling (U.S. & Canada only) (Includes FIRST CLASS POSTAGE) $1.00 per item $ All other countries ($2.00 per item, sea mail) $ ($4.00 per item, air mail) $

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City State Zip Hold it! I ordered two MICRO farads! Number 01 Pins of uc6 I.C. Digitalker Is e1r1 Sockel purcluM MICO OC SSO CMON N P.0 N. 'Rns DYNAMIC RAMS Part No. 'Pins Price Pan No. Rn1 Prke Pan No. Rns Price MICROPROCESSOR CHIPS aids, 1103 16 102481 300ns1 DT1050 Applications: Teaching Pan No. Funnel8 Ria. 99 - 14 25 14 29 59741569 16 59 5N7400N 681742211 4027 16 409681 250ne) ...... 249 appliances, clocks, automotive, telecommunica- 0974019 14 75 14 35 5611157N 16 .59 40 Floppy 0,48 C441589e. 2795 5614739 0765ÁC 41169-2 16 16,3841 1150851 1.89-8/14 95 tions, language translations, etc. 591402h 14 25 5974749 14 35 59741609 16 69 2650 40 MPU 129671 9.95 4116N-3 16 16,38481 (200118) 1 69 8/12 95 5974039 14 25 5971759 16 45 59741619 16 .69 TMS5501 40 Synchronous Data Inlertace (SIRCI 1495 4116N-4 16 16,384111 (25078) 149-8/1095 The 031050 Is a standard DIGITALKER kit encoded with 137 separate 41645150 16 6 9S-8/19 95 5974049 14 25 5974769 16 35 59741629 16 69 MCS6502 40 MPS w/Clock 11 MHz/ 5M 65,53681 (15086) and useful words, 2 tones, and 5 different silence durations. The 41649-200 16 65.53641 (20088) 5.95 8/41 95 5911059 11 25 5974799 11 4 95 59741639 16 69 440565024 44 MPU with Clock and RAM 726974/ 695 words and tones have been assigned discrete addressee, making it 995 MM5261 18 102101 (300n4)300n5) 49 8/1 95 S914069 14 45 5914809 14 89 59 741649 14 69 MCS65028 40 MPU w/Clock at3MHz possible to output single words or words concatenated Into phrases MM52132 21 204841 .. .10 6809 40 CPU (Internal Clock! )MHz 11 95 1 -8-01 The of the 001050 Is a highly in. S97107N 14 29 5N7482N 14 49 59741656 16 69 14915270 18 409641 125075) 9164096 4 95 or even ententes. "volts" output 6809E 40 775-8.57 (Enernal 714481144710 1495 5.174089 14 25 S971639 16 59 59141666 16 89 MM 5280 22 409641 2007s 2107 3 95 lelligible male voice. Female and children's voices can be synthesiz- 8031 a Conte 0rlented CPI/WHAM 81/0 39 95 5974099 14 25 5671859 16 59 59741676 16 2 95 ed. The vocabulary is chosen so that It Is applicable to many pro. 19580359 44 MPU-4.71 5 95 NEW 256K DYNAMIC RAM 5974109 14 25 51774866 14 35 5674170N 16 1 29 ducts and markets. 1245803912 40 CPS -S21 451p8-00(128674 47711) 5 95 14 25 5974896 16 2 75 24 4.95 a Speech Processor Chip, MM54104 -pint 5674119 56141729 19540409-6 40 CPU (256 bytes RAM) 9 95 41256 16 262.144x1 (200ns)....44.95 The DT1050 68,01.88 of (40 14 49 5N74909 14 39 56711136 16 69 1995 two (2) Speaoh ROMs M445218455ß1 and MM52164SSR2 (24.pin) 5974129 19580709 40 774164 bytes RAM) 911452983 16 819241 (20074) 169 and 14 39 11 79 16 69 19980739 40 CPU w/Baste Mkv Imerpreler 29.95 list and a recommended schematic 5974136 591a919 59741749 STATIC RAMS along with 8 Master Word 5974149 14 49 5674929 11 39 56741759 16 69 780856 40 CPU 4 95 diagram on the application 48041. I101 16 25641 1 49 8086 40 CPU 16-61552z 24 95 1650151 SN74169 14 25 597493M 14 39 56741769 14 69 2101 22 25644 (45085)8101 2 49 8088 40 CPU B/16-bit 29 95 5974779 11 25 5974949 14 89 59741779 14 69 2102 16 1024.1 DT1050 Digitalker1M $34.95 ea. 8155 40 3607484)707417-7177641 695 1350710) 16 (450115)5.79 1 59 74206 14 9 597495N 11 49 99741799 16 1 49 21L02 102441 8237 40 Hell Performance Rog DMA Cont. 14 95 MM54104 Processor Chip $14.95 ea. 2111 18 25644 145018)8111 1 959 S674216 11 49 5974969 16 49 59741009 14 69 82375 40 H1gn Pen ßo01394 Cool (57.70) 18.95 2112 16 25644 1450851 905 I 95 9614226 14 49 5974979 16 3 25 59741819 24 1 95 8748 40 HMOS EPROM Mel 24 95 Expands the from 137 to over 260 2114 18 102444 145070) 1 49 8/9.95 1111057- 071050 vocabulary 16 24 1 95 1 19 5974236 59 59141009 99741829 16 21141 18 102484 1450n4ll.P. 195 8/13 95 Z80A, Z808, 18000 SERIES - words. Includes 2 ROMs and specs. 1 -Z80, 5674256 14 29 59141049 14 19 59741846 16 2 49 18 102484 1 75.8/11 95 280 40 CPU (MK38809777807) 2M9z $3 95 21142 (20018) 14 29 11 1 19 16 2 49 2 25 95 Part No. 071057 S24.95 ea. 5974266 59711059 59741859 280-77C 28 taunter Timer C11514í 3 95 21141-2 18 102444 (20075)l .P 8/14 5674276 14 25 54741076 14 .29 59741909 16 69 7800457 40 gal Asynchronous Reg 'Trans 10 95 2147 18 409641 (70851 4 95 2148 18 102484 (707151 4 95 5674286 14 59 547110961 16 .39 56741919 16 69 280 -DMA W 0lreel Me.mry Access 7115117 995 6 iIIL 40 Pa21611101711nace Controller 3.95 TM54045 18 1024x4 (450,4) 3 95 Kiy4(atl4oóts S974309 14 75 59741169 24 1 49 59141929 16 69 Z80 -P10 "Ire 780-510/0 40 5e1741(70)7478 and 48748623e0) 12.95 1371540L47-45 20 102444 1450151 2 95 5674326 14 79 56741216 14 39 59741939 16 69 Pan N4. Pins Function Prim 280510/1 40 Senal l/0 (Lacks 07907 1295 5101 22 25644 (450m) CMOS 295 5N74376 14 25 56741229 11 69 59741949 16 69 280-510/2 40 Sona11/0(Lacks S7NC4) 12 95 MM5257 18 409641 (45085)4044 4 95 70451PI 20 CMOS Precision Timer 14 95 14 56711239 16 49 66141956 16 69 5674389 29 Z80-510/9 40 5ena11/0 12 95 1-196116P-3 24 204888 (150857 CMOS 595 104501(611 28 Stopwatch CIIp. 41L 1995 59 Sel 711259 14 45 $97711969 11 89 9861167-4 24 204848 (200857 CMOS 495 59743951 11 2804 10 CPU IM 634809 997867-1) 0.1114 4 49 71067PL 40 3'h Den 440 9.95 7114611657-4 (17001108) 11 19 56711266 14 45 56741979 11 89 20 Canter Tenet Clmu. 495 24 204848 (200ns)LPCMOS 549 5974406 2804.777 FE02030 354 019(1 L70 Disney for 7106 8 7116 1995 Roc 6M62647.15 28 819240 (150051 CMOS 3695 5914419 16 89 56747326 14 49 56741986 24 1 19 28079ßART 40 Dual 649r/chromes /Trans 9.95 211M62 795 710664 5(15 40 IC, Circuit Board, Replay 34.95 40 Mandy Access Gruel 12.95 16 45 59741366 14 69 56741999 24 1 19 2404-064 Drat 5974429 16 256LP15 / P 4 695 27911 Drive) 11 95 40 Paral91701r/edam Controller 3.95 8 18 5iL S 7107CPL 40 Syr 4/0 (LEO 280Á-1712 5974439 16 125 59741419 16 89 56142219 16 119 7489 16 1644 1 25 2804510/0 40 Sena/1/0(7478.460 6474 9670e3) 12 95 (507813101 7107EV/Kit 10 IC. 7kcu17Board. Disney 2995 125 56744429 16 3 95 16 79 747920 22 25644 (25060) 3 95 S974446 16 59742519 Z804.510/I 40 Sena 50 (tacks PIRA 1295 7116CPL 40 3'h DIg174/2LCD De HLD 16 95 16 69 24 3 95 20 2 49 747921 18 25644 1250174)CMOS 3 95 5974459 S9791439 56142766 2806510/2 40 5en141/0(Lacks. SYNCB) 12 95 12011U5 Low Banery Volt Indicator 2 25 74C929 16 102441 1250n51 CMOS 16501) 3 95 5974466 16 69 59741449 21 3 95 59742199 16 79 2804.510/9 40 Send 1/0 1295 12.95 147930 18 102441 1250751CM05165181 3 95 7205170 24 CMOS LED Slopwatcn/Timer 1 49 995 5974419 16 69 59741459 16 59 567128351 16 2804 40 CR1110K38809-616994 14 745189 16 76x4 13516193105 1 95 7205EV/K15 24 Slapwalcn Cep. OIL 95 28 Counter Uttar Crmuii 12 95 1 19 16 7 95 2809.717 5674489 16 69 59741476 16 59142846 74S200 16 25641 (80714(93410 3.95 Tone 495 2808.0467 40 Dual Asynch Recever/T2nsmlher 1995 720674/PE 16 Generalar 5674509 14 19 59741489 16 1 19 59742856 16 2 95 745206 16 25681 3 95 2808-P10 40 Paral611/O Interlace Corder 12 95 (607193411 7206754/Kit 16 Tone Generator Chip 011 7.95 IN 14 19 59741509 24 119 59143656 16 55 745289 16 1644 2 25 9715 08001 48 775 Segmented 44 95 1357513101 720701/90 14 004111412 70n7188e7 5 95 19 59741519 16 59 56743669 16 55 82510 16 102447 1507510 C 1931151 3 95 5671538 14 14 Fred. Counter Chip, .TL 7 95 SERIES 2 25 72076660411 19 59 16 55 6500/6800/68000 82525 16 1644 15075)0 C (7452891 5671546 14 59741529 14 59743679 CKT 13 95 MC6502A 40 MPU 4.1711 clock and RAM 1247901 6 95 7275170 21 4 Func CMOS Stopwatch 14 25 54741536 16 59 16 55 PROMS/EPROMS 55118599 56/43689 MC6520 40 Peripheral Inter Adapter 4 95 4 Func. 14 95 17024 24 25648 1451 4 95 721506/65 24 Stopwatch Cmp, )(IL 6674606 14 39 571741549 24 1 25 5674390N 16 1 49 MC6800 40 MPU 2 95 2148 24 101488 450751 3 95 7216451 28 801917 Lind Counter C 29 95 7 5974706 14 29 91474155N 16 59 59743939 14 1 49 MC6802CP 40 MPU with clock and RAM 95 27085 24 102488 550174) 5900246 2 95 72160171 28 8 Digit Fran Counter 7.7 1995 eheral40 U xternal Loclon)g 14 95 45085/2716 5 95 MC829E 40 Pe (8711 Adapt( (M7682 2 95 14452516 24 204848 721751 28 4 Digit LEO Up/Down Counter CO. 1095 741500 11 25 7115192 16 79 24 409648 45015) 96172532 695 676828 24 7/14/117 Inlerrup1 Controller 15 95 7M92532 77174171 28 4 01911500 Up/Down Canter C 11 95 '41 551 14 25 7415193 16 79 14 95 9C683018 24 102488.67 ROM (MC68430-4/ 9 95 7492564 28 8192x4 4508S( S51 601 1224171 40 LCD 415 Digit Up Counter DPI 10 95 11 29 7415794 16 69 741992 14 55 MC6850 24 90yngbo8046 Gomm Adapter 7e492776 24 204848 4501573 voltage 9 95 14 25 11 55 7145195 16 69 4 7226400/115 40 5 Function Counter Clip. OIL 74.95 745553 MC6852 24 Synchronous 5etlal Data Adapter 5 75 2716 24 204888 715Onx) 95 1445197 79 14 29 74L595 14 79 14 MC6660 24 06006pá 01 ltal MODEM 7 95 27716 24 204888 CMOS 1995 89 (1356p.1 $9.95 15 14 29 741596 16 74LS221 16 89 MC6890018 61 5490 16.411 (8MHz) 49 95 2716-1 24 20482 3507741 5 95 130009 1983 INTERSIL Data Book 8 14 29 7455107 14 39 7155240 20 1 09 MC68488P 40 General Purpose ln) Adapter 9 95 271605 21 204888 '.550857 4 49 14 29 74/5709 16 39 7415241 20 1 09 MC68652P2 40 Multi. Protocol Comm Controller 24 95 2732 24 409648 450775) fi 95 PRODUCT'"EW 74HC High Speed CMOS 11 19 1 Prop. Ill 95 7115112 16 39 7915242 14 09 MC68661PB 28 Enhanced Comm 273243 24 409608 30085) 7 95 249 59 16 1 95 741606 14117139 14117253 99 1445713 14 39 7445243 14 09 MCM68764 24 646(7906 145075/ 27324.4 24 409648 45085)216 6 95 99 1 1 Perpheral Adapter 95 1.9702 4 59 7467147 B9 14 7445774 14 39 74L5244 20 49 576522 40 Inter 27320.4 24 409648 5507711 5 95 6 1.19 7497251 16 749703 4 75 ]4HC259 16 149 7445122 14 49 7405245 20 1 49 8000 SERIES 27580-4 24 102408 45081) 2 7497157 8 B9 748704 59 7497153 6 .99 74117266 1 19 7415123 16 89 7445747 16 109 2764-4 28 819248 450n8/ 69595 I/ 16580804 40 CPU 295 65 7415125 11 59 7415248 16 1 09 741171101 74717154 4 249 7497273 20 2.89 1958154 40 128 Byte RAM 6.97 I/O 1953 27613 28 819248 S(lOns( 795 148708 99 74117157 14 3.95 14 29 7419126 11 49 7415249 16 109 27C64 n 819248 CMOS 1995 6 09 7406280 8156 40 RAM with l/0 Port and Timer 895 144710 59 74117158 495 4 29 74(5132 14 59 7015257 16 59 24 46006) 21 95 6 89 7016299 20 DP8212 24 AIM Inpul/Output(745412) 2 25 MCM68764 819248 41Sï1 14 29 7115133 16 59 7405253 16 59 45076) 1286 799' /40711 59 77167I60 6 729 7107366 15 239 DP8214 24 7914(77 Intern/pi Cá114 2.95 21128 28 16.38448 EPROM 14 146720 85 7497161 6 1.29 7407367 239 79 7419257 1. - II 7115136 14 39 16 59 745188 16 3288 PROM 0 C (6330 DP8216 16 a79rec11onal Bus Elmer 1 95 746720 59 74117162 20 14 29 7415138 16 89 7455258 15 59 I 6 129 7497373 239 DP8224 16 Clock Generator/Dr9er 2 25 746287 16 25644 PROM 7 5 (6301 08 14 35 71L539 16 19 7415260 11494 149727 59 74117163 6 129 7497374 20 239 DP8226 16 Bus 0nve- 2 25 749288 16 3288 PROM 7 5.16331-I 149730 69 70X6164 1.29 74117390 16 1.9 30 14 29 74L5151 16 59 7415266 659 745387 16 25644 7404 0.7.(6300 II 4 DPB228 28 594117771 Cant/ 5715 Driver 174542737 3.49 ;4HC32 75 1 74117393 14 149 14 39 7415153 16 59 7445273 20 49 746177 20 25648 PROM T.5. 16309.11 74117165 8 279 09823B 28 System Calmer 1749438) 449 148L41 99 73 14 55 1aLS754 24 1 29 7415279 16 49 7497166 6 795 74117533 20 239 958243 24 I/O Expander la 48 5er140 3.95 745472 20 51248 PROM T 9 16349-11 710757 75 20 2.39 14 35 74LS155 16 69 7115283 16 69 745473 PROM 0 C 74117171 6 169 7497534 NS8245 18 16 -Key Keyboard Encoder 1717922) 4 49 20 51748 (6348) 8 7415290 7791758 75 77617174 6 7497595 16 395 11 35 1445156 16 69 14 89 745474 21 51248 PROM T 5 12618752969 99 N58246 20 4% 6773 79 461 16 29 7415157 16 69 7115293 14 79 51258 PROM 7467175 0 99 14710.688 20 319 658247 28 98pey 787179dler 774CC11C92319111) 895 749475 24 0.0 16340) 16 55 1415158 16 59 741S298 16 89 749774 /9 7480192 0 139 71974002 4 59 658248 28 Display Con7red1747972) 895 745476 18 102144 PROM T 1 1411775 89 749074017 6 16 75 7415760 16 69 7419352 16 29 745478 24 102408 PROM T 5 7197193 1 139 219 N582509 40 Asyn Comm Bement 1095 7171776 49 75 1 79 74XC4020 6 39 16 7415761 16 69 7415353 16 29 749570 16 51284 PROM 0 C (6305/ 7467191 / 109 064257 28 Rog Clem 170 (USARTI 49 159 9 14 75 7415162 16 69 7415365 16 49 149785 7497195 1 1.09 74974024 4 1 59 DP8253 24 Pre Interval Toer 695 745571 16 51244 PROM 1 5 163061 746786 69 74974040 6 1.39 14 25 7415163 16 69 7419366 16 49 715572 18 102444 PROM 0 C 163521 1480237 / 1.95 074255 40 Rog Penpnerel/0(PPI) 4 49 7467107 59 14 25 1415164 14 69 7015367 16 49 T 1017240 20 195 741174060 5 139 102484 PROM S - DP8257 40 Rog DMA Coded 5 95 745573 18 )8251371 74117103 79 4 59 5 14 29 7415165 16 I 19 7415368 16 49 PROM C 1497741 al 195 74674075 074259 28 Rog lnlerm9 Control 695 82523 16 3208 0 1275181 I 49 74117112 79 77917241 74979078 4 69 11 39 1455168 16 '9 741.5373 20 825115 24 51288 PROM1 5 (279151 14 195 074215 40 Rog CRT Coned 29 95 1460113 79 14 49 7415169 16 7415374 20 1 49 7467243 11 195 74674511 6 269 OP8279 40 Rog Key6 4100389äy menace 895 825123 16 3288 1260917 5 (27919) 1467725 99 74117244 74974514 4 3 79 15 39 7415170 16 49 7415375 16 69 825126 16 25684 PROM 0 C (275201 29 1.95 8284 18 Clock Generalor/Onw1 650 45 2 99 77917215 2 74974538 6 39 16 39 7415113 16 69 74L5386 14 825129 16 25644 PROM T S 127521) 20 49 8288 20 Bus Canlrol/l 995 195 IN 14 1415393 14 1 19 6 1417751 IB 89 71974503 6 349 39 7115174 16 69 825130 15 51284 PRDM 0 C (275121 076303 20 8-88770$747ea-51e414441 Trans 395 16 65 7415175 16 65 7419399 16 1 49 8 109 7497004 I0 unbullered. All olherS are buffered Receiver 295 825185 18 204844 PROM T S 178724581/ 16 7415610 I 49 DP8304 20 8-dl8/brec/lone 89 7.15181 24 2 9) 16 825191 24 204848 180851 DP8307 20 8.64 B1-01rec1859 Realver 295 14 1 49 747221 16 195 7445190 16 85 811595 20 068770806 24 102448 PROM O. C. (8251801 /4700 35 74C-C/MOS DP8304 20 B-144 81-01ret18741 Receiver 295 1 811597 1 49 747240 20 95 7415191 16 8. 20 102488 PROM T 5.(8251811 74602 Latched Pend/dal Omer 495 D58751819 24 DP8310 20 Octal 74704 14 29 74C95 14 39 746244 1 95 08879184N 18 204844 PROM 0 C 1825184) 8741 40 8.18101114 Penrehe7al lnlenare 29 95 740373 26 2 49 74S/PROMS' 745243 14 49 0847578524 18 2048x4 PROM if 5 1020185) 74708 14 35 747107 14 89 74C10 14 35 16 49 747374 20 2 49 2 49 DISK CONTROLLERS 24 204844 PROM 0.0 1826190) 747151 14 35 745244 20 098751909 14 1951771-1 40 51198 Density 1695 24 5191 74.779 14 69 747754 14 49 747901 59 14 35 745114 14 749251 16 9 DM8151919 29 74720 14 35 747157 16 25 747903 14 59 F01791 W 51/91/0191 Gen./ (Im / 95 DATA ACQUISITION 14 45 745/33 16 55 45253 16 1 19 74730 14 35 747160 16 19 74C906 14 59 F21793 40 Singh/Dade Density(True) 29 95 0710 Moslek DC/DC Convert 51/ -911 14 45 745134 16 5( 740257 15 19 74732 14 39 747161 16 19 746911 28 895 F121795 40 Dual Densre/Side 98at(Inv.) 29 95 84734707 18 Floppy Disk Read AMP System 11 745735 True 79 /4742 16 139 747162 16 19 747912 28 8 95 39 15 69 ]45258 16 119 F21797 10 Dual Denser/See Seed 95 MC1408L7 167-0110/A Converter 10ACOB07LC91 1 19 1 746915 10 1 74748 16 95 747163 16 19 14 39 745136 14 39 745260 14 1 19 MC7108L8 16 8.611 D/A Convener SPECIAL FUNCTION 104C013081C9/ 747917 28 895 4270803LCN 1/21067 74773 14 79 717164 14 49 14 35 746738 16 89 745280 14 1 95 195 708-6IA/O Converters 050026C9 8 Dual MOS Clair Omer 15957 14674 11 69 16 19 746922 10 4 49 0070604 208-0nA/D Convener 11L51( 747773 14 35 745139 16 89 745287 16 1 95 I952651 28 Communirallon Clip 895 74725 16 195 747174 16 19 746923 25 4 9'. 04C0806 16 B-0110/6 Converter (0 78% Lm 1 14 35 745140 14 745288 16 1 95 M73470P 15 Floppy 958 Pee Amp SYslem 495 4286 14 39 747175 16 19 746925 16 5 95 ADC0809 288-611 A/D Converter (8 -Ch Muth1 14 35 745151 18 99 745373 2 49 4444542409 24 Asynchronous 6ansmmel/4ecener 595 16 5 7- 16 49 74C926 18 595 20 A070817 40 8.61 A/D -Ch 94111 747192 Convener /16 65 74 35 745153 16 99 745374 20 2 49 91M54167414 24 Meloprocessv Real Time Clock 8 95 14 747193 16 69 80795 16 2717 1000 24 105110/A Cony. Mena Comp 10 05°- 619158104AN 16 Micro Compatible Tare Clock 7 95 740195 16 39 80697 16 69 745-- 14 35 746157 16 99 745387' 16 1 95 DAC1008 2010-bi10/A Cony. Micro. Comp. (0 20.. COMM 40 96 74007719er 47/6.991 RAM 595 7893` 14 45 745158 16 99 745471 20 5 95 DAL1020 1610-6110/4 Cony (0.05% Lin ) 477 pral LEO fee 745160 16 2 49 0471022 1610-61D/A Cony 11071CP 9 1171741761 35 74538 14 89 745472 20 a.95 COP40269 10 M6roprocessaw/ú4E90 PAM 595 (0.20%Lin 0471222 1812-0110/4 Cony (0.20% ten 1 IL072CP 139 LINEAR LM747M 69 780 14 39 745174 16 19 745473 20 95 6 91471 LEO Done 7.4/6 Buss Inl LM33 2 Constant Curren) Source 1107479 I 195 1117489 55 7455151 14 35 745775 16 79 145474 24 495 C0P4706 20 32 -sag VAC Fluor 9vr. 120 -pin pkg.) 3.25 L83352 Temperalure Transducer 7L087CP 59 LM342P.5 69 19113106 149 74564 14 39 745188 16 43 745475' 24 4 95 M85369Á4/9 5 P7og 0sc111ator/O1v13er (609:1 179 L613995 Temp Comp 7rec Ref .4 5ppm/C°) 5.00 69 MM5369E5T 8 Rog 0sc0Mtor/Diader110071z( 195 11082617 1 19 LM342P-12 A1LI33073 74565 14 39 745194 16 49 745570 16 2 95 An-5.1O13Á 40 306 Baud 60117915425 .3.95 TL084C9 1 195 1M042P-15 69 MC1349 179 74574 14 55 715795 16 49 745571 16 295 I 149 L60301CN 35 1.73476 061350 1 49 74585 15 1 19 745196 14 49 745572 18 1 95 LOW PROFILE .W SOLDERTAIL 11713021 195 1613939 I MC1356 95 74566 14 55 745240 20 25 745573 18 4 95 (TIN) SOCKETS STANDARD (TIN) LM304H 195 4A4350K 4.95 LM1456V 745112 16 55 745241 20 25 7.5940 20 219 LF351N 60 1.9 10.99 100.up 49 10.99 100.up 1830571 99 1rA1458011 59 745113 14 55 745212 14 49 745941 20 2 49 LM307CN 45 073530 100 1M1488N 69 LP LF355N 110 8 pIn LP .16 .14 .13 14 pin ST 29 -27 25 1.51308139 69 LM1489N 85 CA30109 135 11:tMINj1a:eM 17356N 1.10 195 003130E 8 B9 14 pin LP 17 .15 .14 16 pin ST .34 .32 30 LM309K 1.25 517114969 7430399 1 35 16 99 1.79 LM'358N 69 1H160.5CK 995 7130819 743140E 8 79 16 pin LP 19 17 .16 18 pin ST 38 .36 LM370CN 7430469 14 135 16 119 743160H 1.95 117131106 69 1913596 I 1 19 LM1800N 249 7630026 18 pin LP 26 .24 .23 20 pin ST .45 .43 .41 14 2 95 1613706 1 449 LM1871N 295 CA30599 7430839 16 1 49 743161E 16 2 95 LM312H 249 20 On LP 30 .27 .25 20 pin ST 49 46 43 I 195 7430609 16 1 95 7530069 14 69 7A31620 16 6 95 LM3177 119 143139 1/41872N 325 22 pin LP 31 .28 .26 28 pin ST .69 .67 .63 LM377N 1 195 603055E 14 7.49 CA3189E 16 1 59 LM317K 395 1M1877N-9 209 7630699 16 163 33 24 pin LP .30 .28 40 pin ST 99 .95 .89 LIA180f,14 1.10 663080E 8 89 C0731019 14 59 LM3187N 1 195 11A1M9N 225 7430966 16 1.09 28 pin LP 10 .37 35 SG LM319H 14 1.95 1143809 I 69 4.34189611 2.95 LP WIRE WRAP SOCKETS 36 pin 46 42 39 1 1.79 723098 16 95 LM320K-5 1.35 LM381N 16120321 195 CD-CMOS 40 pin 49 704000 14 19 LP 46 .43 (GOLD) LEVEL #3 1438218 1 139 604506 16 19 LM320K12 135 3.420036 89 CD4001 11 .29 1IN320K-15 1613846 1 1.79 )(R2206 395 704040 16 ¡ 9 704507 14 19 49 10.99 100.up 135 704002 11 29 SOLDERTAIL (GOLD) LM320K-24 135 Lf4386f1-3 89 532207 295 704041 14 9 CD1508 24 95 704006 14 I 19 5 pin PM 49 .45 42 LM320i-5 .89 06L367N 89 xH2208 249 CD4042 16 29 CD151D 16 29 STANDARD lo pin WW .62 .59 583896 1 119 C23007 14 29 1.9 1999 100 -up 'filer .65 W3201 .I2 89 1f32211 395 704043 16 /9 704511 16 19 CD4009 16 .59 14 pin WW .65 62 .59 1M320T-15 69 543919-80 I 1.19 182877P 195 704044 16 79 701512 16 19 ST 69 CUM 16 59 S pin SG .30 .27 .25 16 pin WW .69 .65 61 LM320i-24 19 1613929 LM2878F 7 19 704046 16 704514 24 49 56139819 395 14 59 704077 14 29 14 pin SO .43 .39 37 16 pin WW .69 .85 ]9 163228 14 165 51429019 1 49 CD4047 14 29 701515 24 117132311 5.95 16139911 500 LM2902N M 89 C01012 14 29 16 pin 95 .47 43 41 20 pin WW 1.09 1.05 99 004040 16 59 C04516 16 19 1M324M I4 59 71494014 I 395 16129079 11 14 704013 14 39 18 pIn SG .53 .49 .47 22 pin WW 1.25 1.19 1.15 701049 16 .39 604518 16 19 71496CP 1.19 59 24 pin SG 65 LM3290Z 65 LM3900N II C04014 16 1 19 .69 .61 24 pin WW 1.29 1.23 1.15 724050 16 39 C04519 16 59 1613319 ] 95 NE537V 295 1M3905CN 1 115 CD4015 16 .39 28 pin SG Al 76 72 28 pin WW 1.59 1.50 1.15 704057 16 99 704520 16 19 1603342 119 NE544N I 295 1M3909N 8 99 14 49 36 pIn SG 1.09 1.03 .97 36 pin WW 1.85 1,75 1.69 C04016 675504 I 195 16 99 C 04526 16 19 Y1W 1174,335.7 140 LM3914N 11 251 CD4052 40 pin SG 1.21 1.14 723077 16 1 79 1.08 40 pin WW 1.99 1.89 1.79 NE555V 35 721053 16 89 704528 16 49 LM3362 119 1.9139159 18 295 704076 16 99 LM337MP 1 15 %R.L555 59 LM3916N 14 295 C04056 16 2 95 704529 16 69 U.S. Funds Only Spec Sheets 30e each 701019 16 59 610.00 Minimum Order - 4M556N 1 69 8 125 - LM337T 795 9(41369 C0.059 21 7 95 004543 16 95 es Tax Send Postage for your NE564N I 704020 16 119 California Residents Add 6'/a % Sa $1.00 LM338K 695 295 374151X8 / 1 95 704060 16 119 14 95 024562 1615659I 1,19 724021 16 1 19 Add 5% plus $1.50 Insurance FREE 1984 JAMECO CATALOG LM339N 14 69 8C81947K 14, 1714066 11 19 16 Shipping - C23566 39 L6566711 1.49 724022 16 1 19 Prices Subject to Change LM340K-5 135 R74195T1( 704068 14 39 CD4583 16 49 Send S.A.S.E. for Monthly Sales Flyer! 704023 14 29 16C140K12 135 16156717 99 L1M250CN 125

14 29 704584 14 I C04069 69 L4340K15 1.35 1165706 395 L1M50W 10 k5- C01021 11 69 Mall Order E1ac7ronicsWorltlwitle 7D4070 14 39 704723 16 19 LM340K24 135 171E5719 I 295 6E5532 ; 45 704025 14 23 C04011 14 29 704724 16 19 16134075 79 54770304 1.19 NE5534 9 704026 16 2 49 Cg4012 14 29 MC11409 16 95 51713407.12 79 16470911 49 ]9M05 69 [23027 16 5 704013 14 29 MC19410 16 95 (MasterCard LM140i-15 79 501104 69 creme ; 395 701028 16 69 16 aaimeco 79 1517119 19 119 1M390T-24 15132906 129 CD4015 29 MC14411 24 95 704029 16 LA4113N 55 119 704076 16 7 19 MC11412 16 95 LM341P-5 75 LM13600N C04030 14 39 ELECTRONICS 100 704078 14 49 MC144t9 16 95 5M341P-12 75 16173361 28 704034 24 2 49 LM739N 195 A6MAM3 CD1067 11 MC14433 24 95 Lktl91P-15 75 HORE 724035 16 149 1355 SHOREWAY ROAD, BELMONT, CA 94002 704082 14 29 MC14538 16 19 IMoro in Catalog) 30003 1982 Nat. Linear Data Book 11952 p9s 1 .511.95 604093 14 49 MC14541 11 19 10/84 PHONE ORDERS WELCOME - (415) 592.8097 Telex: 176043 CIRCLE 212 ON FREE INFORMATION CARD Radio - Electronics HufIwarü 51iitw

New for our readers....A mailorder source of software for Atari 400, Atari 800, IBM P C, Commodore VIC-20, Apple II, and other personal computer systems.

IBM PC APPLE COMMODORE VIC-20

-1 FLIGHT SIMULATOR by Mi- PRISONER2 by Interactive J PIPES by Creative Software F.S'i SrÁñ:ttM crosoft ... List $49.95. Our price Fantasies ... List $32.95. Our ... List $39.95. Our price ...... $43.00. Highly accurate sim- price ... $28.00. Escape is $34.00. Connect a pipeline ulation of flight in a single -engine hardly possible. The island from the water supply tank to aircraft. Working instruments. keeps you under surveillance. every house. Watch out for Out the window graphics. Real- Just try and get out! (Apple II, leaks. Use as little pipe as time flight conditions. (IBM P C, 48k, disc) possible. 5 skill levels. (Com- 64k, color graphics, disc) PRISONER2 by Interac- modore VIC-20 cartridge) tive Fantasies ... List $39.95. Our price ... $34.00. (Atari SHAMUS by Human En- EASYWRITER II by In- disc) gineered Software ... List formation Unlimited ... List $39.94. Our price ... $34.00. THE MASK OF THE SUN $350.00. Our price ... Only you can stop the Shad- by Ultrasoft Inc ... List $39.95. $300.00. Turns your com- ow's mad reign of terror. Two Our price ... $34.00. An ani- puter into a word levels with 20 rooms each. A mated adventure through a processor. You see every- joystick challenge. (Com- series of hi -res screens. An thing the screen. There modore VIC-20 cartridge) on ultimate adventure challenge. are no imbedded com- (Apple II, 48k, disc) mands. (IBM P C, disc) HOUSEHOLD FINANCE 1-1 DEADLINE by In- by Creative Software ... List focom ... List $49.95. $17.95. Our price ... $15.00. adl MASTERTYPE by Lighting Our price ... $43.00. A ,,.,..,.... Home utility program records Software ... List $39.95. Our locked door. A dead and analyzes your monthly in- price ... $34.00. A typing in- man. You have 12 come, expenses and budget in ikottio' struction system in an exciting hours to solve the mys- leg 16 categories. (Commodore hi -res game format. Learn to tery. One false move, VIC-20 tape cassette) type while battling waves of and the killer strikes attacking enemy words. (Apple HOME OFFICE by Creative again. (IBM P C, 48k, II, 48k/64k, disc) Software ... List $29.95. Our . disc) leIORM price ... $25.00. Combines VICPRO, a flexible and effi- ALGEBRA, Vol. 1 Edu- by cient word processor with ware ... List $39.95. Our price THE GRAPHICS MAGI- VICDATA a powerful and so- ... first CIAN by Penguin Software ... $34.00. A year algebra phisticated information storage definitions, List $59.95. Our price ... tutorial covering and retrieval system. (Com- number line sets, $53.00. Make your own ani- operations, modore VIC-20, cassette tape, P 48k, color mated graphics. Handles up to etc. (IBM C, 8k additional memory required) grpahics, disc) 32 independent objects. Stores hundreds of color pictures. (Apple II, 48k, disc) ATARI

I SUBMARINE COM- MANDER by Thorn EMI ... List MICRO/TERMINAL by RENDEZVOUS by Edu- $49.95. Our price ... $43.00. A MICROCOM Microcom ... List $94.95. Our ware ... List $39.95. Our price submarine patrol simulator to price ... $83.00. Allows ac- ... $34.00. In four phases, sim- hunt and destroy enemy ships. cess to remote mainframes ulates an actual space -shuttle 9 skill levels. Plug-in cartridge. flight from Earth Liftoff through and minis, information data (Atari Cartridge 400/800) banks, and other personal Orbital Rendezvous and Ap- computers. (IBM P C, disc) proach to Alignment Docking with a space station. Hi-rez 1N31 want graphics II, (Apple disc) APPLE MINER 2049 by MicroLab PC TUTOR ... List $39.95. Our price ... PC TUTOR by Comprehen- SAT WORD ATTACK $34.00. Chase into a Ura- sive Software ... List $79.95. SKILLS by Eduware ... List nium mine thru 10 levels of Our price ... $69.00. Interactive price ... $43.00. A $49.00. Our traps and capture Yukon program teaches you how to tutorial for vocabu- mastering Yohan. Scale ladders, jump use your IBM Personal Com- lary, new deciphering or from moving platforms, and puter, including hardware and unfamiliar words, and taking win-if you can. (Apple II, software. (IBM P C, 64k, disc) tests. (Apple II, disc) 48k, disc) J Radio -Electronics Software Store 200 Park Avenue South AN5 New York, NY 10003

Name Number of items ordered ri Total Price of Software $ Address Sales Tax (NY State Residents Must Include) City State 71P Shipping ($2.00 per item)

TOTAL ENCLOSED (Sorry. No COD's) $ SORRY - NO CREDIT CARD OR COD ORDERS

CABLE -TV Moo «I» *V» PRICE SLASH! . -- OUTPUT CHANNEL (Circle the one used ITEM on your system) REG. NOW QTY. PRICE JERROLD 400 CONVERTER (58 CH.) CH. 2 CH. 3 109.00 90.00 (10 or more) CH. 2 CH. 3 82.00 75.00 JERROLD 450 CONVERTER (66 CH.) CH. 2 CH. 3 134.00 105.00 (10 or more) CH. 2 CH. 3 110.00 90.00 EAGLE COMTRONICS 400 MHz CONVERTER CH. 2 CH. 3 109.00 90.00 (10 or more) CH. 2 CH. 3 82.00 75.00 SB ADD-ON UNIT CH. 2 CH. 3 129.00 99.00 (10 or more) - CH. 2 CH. 3 79.00 58.00 BRAND SB TRIMODE COMPLETE UNIT CH. 2 CH. 3 Please call for price NEW SB TRIMODE CONVERSION KIT CH. 2 CH. 3 quotes and details. MINICODE (N-12) CH. 2 CH. 3 109.00 89.00 (10 or more) CH. 2 CH. 3 79.00 56,00 MINICODE (N-12) VARISYNC CH. 2 CH. 3 119.00 99.00 (10 or more) CH. 2 CH. 3 86.00 62.00 C-1000 ADD-ON (COMPATIBLE -ALL ZENITH SYSTEMS) CH. 2 CH. 3 260.00 225.00 (5 or more) CH. 2 CH. 3 220.00 185.00 MLD-1200-3 CH. 3 ONLY 129.00 99.00 (10 or more) CH. 3 ONLY 85.00 58.00

IMPORTANT: WHEN CALLING FOR INFORMATION - Please have ready the make and model # o' the equipment used in your area. Thank You

Name Sub -Total

Street Shipping

City/State/Zip TOTAL

Phone Number Area Code Number

Sale of De- MUST BE SIGNED AND RETURNED WITH YOUR ORDER Add $2.00 per unit ship - scramblers I understand that the purchase of these cable T.V. products does not authorize their ping or call may be pro- use on any cable T.V. system. I agree to obtain the proper authorization from local for specifics. hibited in officials or cable company officials in my area. Paymentis some states. accepted by Signed If in doubt, money order or check with Cashier's check local author- only. COD's & Hies. No Transamerican Cable Distributors ó acceptit ed as Ohio orders our low prices accepted. 449 BROADWAY AVE. BEDFORD, OHIO 44146 (818) 956-5839 prohibit their use. Please -No Collect Calls

9 The case measures 173/4 x 123/4 x 61/2 NEW PRODUCTS inches and also features two removable gate - swing pallets. That permits easy access to continued from page 6 tools, parts, and equipment carried in the case bottom. The model JTK-87 is available with a selection of over 100 tools, and is COLOR -VIDEO CAMERA, model CV-301, priced at $509.00. The portfolio case only is weighs 1.6 lbs and is compatible with all VHS - priced at $189.00-Jensen Tools, Inc., 7815 format video -cassette recorders. It is adapta- South 46th St., Phoenix, AZ 85040. ble to Beta -format video -cassette recorders with a standard adapter cable. POWER SUPPLIES, the PAB-A series, featuring 31/2 -digit LED readouts that are green in the voltage mode and red in the current mode. They are available in five models, with outputs ranging from 350 volts at 0.2 amperes to 5.0 amperes at 8 volts, with 0.02% regulation. CIRCLE 239 ON FREE INFORMATION CARD

and magnetic head -speed detection. The model DP-15F has a suggested list price of $199.00.-Denon America, Inc., 27 Law Drive, Fairfield, NJ 07006. SIGNAL GENERATOR, the model LSG -215A, is a programmable synthesized AM/FM RF signal generator featuring convenient keyboard control of frequency and output level. Semi -automatic operation is available by pre-programming up to 100 different test conditions. Two kilobytes of memo- CIRCLE 236 ON FREE INFORMATION CARD ry stores frequency, output level, and modulation data for each test condition. The unit delivers horizontal resolution of The model LSG -215A offers an output -fre- 270 lines; a minimum required luminance of quency range of 0.1 to 120 MHz in two bands: 35 Lux; image signal-to-noise ratio of 45 dB; 0.1 to 30 MHz in 100 -Hz steps, and 30 to 120 video -output signal of 1.0 -volt p -p/75 ohms, CIRCLE 237 ON FREE INFORMATION CARD and an audio -output level of -20 dB (1000 ohms). The features include constant -voltage or con- Other features of the model CV -301 include stant -current operation; remote -voltage pro- a unidirectional electret condenser micro- gramming; overcurrent protection; series or phone, and f/1.5 manual 3 -to -1 zoom lens parallel operation; auto -ranging in voltage with 10 - 30mm focal length, a through -the - mode, and independent external -voltage lens optical viewfinder with in -finder LED to readout using the supply's digital meter. indicate recording low -light and power warn- The PAB-A series has a design MTBF of CIRCLE 240 ON FREE INFORMATION CARD ings, and a light balance control to match four over 10,000 hours, and prices range from separate color temperatures. $175.00 to $350.00.-Kikusui International MHz in 1 -kHz steps. Output -level range is The model CV -301 has a suggested retail Corporation, 17819 South Figuerola St., -10 to 120 dBµvolt in 1 -dB steps. price of $795.00.-Konica, Konishiroku Gardenia, CA 90248. The model LSG -215A is designed par- Photo Inc. USA Inc., 440 Sylvan Avenue, ticularly for use in the communications indus- Englewood, Cliffs, NJ 07632. try, but is a general-purpose signal generator DIRECT -DRIVE TURNTABLE, model as well. It is priced at $2,795.00.-Leader TOOL KIT, model JTK-87, is a deep poly- DP -15F is a complete non -contact system Instruments Corporation, 386 Oser Ave- ethylene case with a removable document that senses and corrects for record imperfec- nue, Hauppauge, LI, NY 11788. R -E portfolio. A recess in the outside of the lid tions such as warps. The tonearm provides accommodates a locking, black, vinyl port- for improved tonearm/cartridge matching, be- UNINTERRUPTIBLE POWER SYSTEM, the folio for documents and schematics. It is se- cause it responds to the combined tonearm/ LINE -SAVER'- , model LS -240, is a standby cured to the lid with velcro fasteners, and can cartridge mass. system for use in the home and small-busi- be detached when necessary to do paper- The DP -15F has a flat -twin direct -drive ness computer market. It is available for work while traveling, or slipped into the case motor, microprocessor -controlled automatic 120/240 volt, 60/50Hz systems, and has 240 - for shipping. operation with front -panel soft-touch controls, VA, 150 watt capacity. The unit uses pulse - width modulation (PWM) technology to regu- CIRCLE 238 ON FREE INFORMATION CARD late the AC output voltage for greater efficiency to various load conditions. The PWM-AC output will also increase battery efficiency to continued on page 13

CIRCLE 241 ON FREE INFORMATION CARD

10 itk

pacesetter in 3

R-11 portable receiver

reach out and bring in those distant Optional HS -7 micro -head phones stations from all over the world. a low for priva.e listening pleasure. Simplicity of operation is enhanced All this along with a record output Kenwood's P-11 is the perfect "go by a band -spread type tuning ack, external antenna terminal and anywhere" portably, receiver. It control. Electronic band switching, a rugged and attractive carrying covers the standard AM and FM with LED band indicator, along with case make the R-11 portable Broadcast bands plus nine addi- a tuning meter to ndicate received race ver the perfect travel tional short wave bands, The R -11's signal strength, combine to provide corn minion! selectivity is greatly enhanced by you with superior listening capability. More informat.on on the the use of double -conversion on Safety Hold -Release switch prevents Kenwood receivers is available short wave frequencies above accidental station loss. Large front from authorized dealers of 5.95 -MHz High sensitivity coupled mounted speaker provides excellent T`io-Kenwood Communications with a dual antenna system (tele- sound'' quality. Tone switch adjusts 1111 West Walnut Street, scopic and ferrite core) allow it to for high, low and voice transmission. Compton, CA 90220.

litt 1/0 7 7 7 1771 - -- - - ` r R -2000 -op -of -thu-line general R-1000 High performance receiver R-600 General coverage receiver coverage receiver - 150 kHz to 30 MHz 200 kHz 30 MHz digital display/ 150 kHz -30MHz digital display Ten memories Dsn 24 -hr clock with clock(timer 3 IF filters PLL UP con- 2 !F liters PLL UP conversion noise tmerSc .(' ^' ?-.,° VAC (Opt.1:3.8 version noise blanker RE step atten- beanf,s,,r RF attenu-='or front speaker VDC) C z converter). uator 120-240 VAC (Optional 13.8 VDC). 100-240 VAC C Ial 13.8 VDC).

SW l SW2 SW3 fW4 SW6 ìW] 918 SW9 MW

14.8 lis 88

1.45 US 13.95 1555 185 74 9.8 13.9 155 1.9

13.8 1 18

13.15 S35 7.75 .....e...... 13.7 52 1.1 ...... 13.95 1525 7.65 95 .ee.eee 133 I51 1,g 945 ...... 1355 15 1s -1.55 9.4 ...... 1. 135 Si1 515 .1...... /../....e... .11..././ 1.55 ..55.55...... 1.... ue...... 1...///...e....5.. O...ee5.O.5..e....11.1.515155 TUNING

ANns RECEIVER R-11

CIRCLE 213 ON FREE INFORMATION CARD COLLAC'TORS PREMIER EDITION LOOK FOR OUR From ItTe of $2.50 U.S Radio -Electronics SUMMER 1984 $295 CANADA NEW NAME! afl s o Electiorncs 48784 HANDS-ON THE MAGAZINE FOR THE ELECTRONICS ACTIVIST, The Great Pewee Supply bsue! ELECTRONICS sad the DUAL POWER SUPPLY FORMERLY TiPs on DESIGNING SUPPLIES SPECIAL PROJECTS

Complete plans Ar- Get every issue! AUDIO BOOSTER AMP ELECTRONIC CROSSOVER °" ri DIGITAL AUTOTACH SUBSCRIBE * rkssaAç

AALCULATOK-analog computer measures blood alcohol level TODAY! TONE RINGER-Replace your phone's bells with a warbling tone UPGRADE RAM/DISK-Speed up disk data retrieving and stoning ide I¡ Resistor [Sank for rapid ohmi. substitution Use the order o @) Breakout Box brings R back to standairt Solar Cell Converter stetas up the toltage 7,96 form below.

Subscribe Today! tronics will continue to contain a variety of construction articles to suit every IF YOU'RE THE KIND OF READER TO HELP YOU TO BE SURE that you taste. In addition, feature articles on that doesn't want to wait, you can order don't miss any future issues of Hands- electronics fundamentals, test equip- your next copy of Hands-on Elec- on Electronics-SUBSCRIPTIONS ment and tools will round out each issue. tronics now. Hands-on Electronics is ARE NOW AVAILABLE! Of course, Hands-on Electronics will crammed full of electronic projects that continue to provide new product and lit- you won't be able to wait to build for YOU CAN HAVE THE NEXT FOUR erature listings to keep you up to date on yourself. You can expect top-notch digi- ISSUES of Hands-on Electronics de- the latest developments in electronic tal projects, fun-to-plaÿ electronic livered directly to your home for only technology. games, valuable add-on computer proj- $10.00. We pay the postage. If you want ects, BOB and shortwave receivers, the next eight issues, you can even save GET IN ON THE ACTION! Order photographic/darkroom gadgets, de- a dollar off the newsstand price. Get your next issue of Hands-on Elec- vices to improve your car's performance, eight issues for $19.00 tronics today. Use the convenient order test equipment ideas, and more in every coupon below. Be sure to send check or issue of Hands-on Electronics. EVERY ISSUE OF Hands-on Elec- money order-no cash! r Detach and mail today to: CASH WITH ORDER ONLY AANN5 Allow 6-8 weeks for the first issue to arrive. Hands-on HANDS-ON ELECTRONICS Electronics SUBSCRIPTION DEPT. Please print P.O. BOX 338 SUBSCRIPTION MOUNT MORRIS, IL 61054

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I want to be sure I don't miss any issues and want to save $1.00 too. Send me the next eight issues of Hands-on Electronics for $19.00: starting with (Street Address) #2. Postage is free in U.S. For Canada add $4.00. Foreign add $14.00. CI Send me copies of Hands-on Electronics #2 at $2.50 plus $1.00 postage and handling for U.S., Canada and Mexico $1.00 per copy. U.S. funds only. (City) (State) (Zip) L J

12 NEW PRODUCTS ceivers, the range is about 35 feet. The system can be used for either stereo or mono. continued from page 10 The stereo headphones, model IRH-210 have full frequency response, 50-15,000 Hz. The infrared sensor is on top of the head- increase back-up time: 5-10 minutes full load, phones for optimum reception. Any number 20-25 minutes half load, 35-40 minutes 1/3 of headphones can be used with the IRT-200 load. transmitter. In addition there is an internal 12 -volt sea- The IRSR-220 infrared stereo receiver led rechargeable battery, four voltage-surge works with any stereo earphones. Two can protected and EMI/RFI filtered AC outlets, listen at once with the unit, which can be audible and visual power-failure warnings placed up to 35 feet from the audio -source/ systems, test -mode indicator and switch, and IRT-200 transmitter hookup. replaceable external fuses. The system has a retail price of under The unit comes complete with a 6 -foot, de- CIRCLE 243 ON FREE INFORMATION CARD $100.00.-Nady Systems, 1145 65th Street, tachable, 3 -prong, heavy-duty cord -set with a Oakland, CA 94608. R -E 40 -pin DIP clip. A special plug-in module adapts the unit so that it is suitable for use with most microprocessors. There are seven output jacks on the front A QUALITY TRIPLE -REGULATED panel for monitoring pulse duration and timing relationships with an oscilloscope. There are sixteen input lines and six user-definable POWER SUPPLY AT A LOW, control lines. Addtrace 1 is available in kit form for NOT A $199.95. (Factory -wired prices are available LOW PRICE!! on request.)-BMH Company, Inc., 224 Vas- KIT! sar Street, Reno, NV 89502.

TWO-WAY FM RADIOS, the basic medium - power Midland SYN- TECH mobiles and base stations have had their transmit and receive bandwidths increased. The bandwidth of the 50 -watt low -band (29-54 MHz) VHF models is being doubled

from 1 MHz to 2 MHz. The 40 -watt mid -band (66-88 MHz) models will have an increased bandwidth from 2 MHz standard to 8 MHz (transmit) and 3 MHz (receive). MODEL PS101 This DC triple regulated variable power supply FULLY ASSEMBLED & TESTED! has all the features you could ask for plus a full 1 year guarantee. Fully adjustable from 1'/a VDC to 35 VDC( Three completely independent supplies that offer many advantages! They can be either a pos. supply or a neg. supply...they can also be stacked in series so that a 5V and two 15V sup- S 88 plies can total a 35 VDC supply or any combina- FULL 1 tion of the three...(after one of the terminals is YEAR grounded to give it a reference)...for the first time REPLACE- you can now purchase this American made fully MENT adjustable power supply at a price that is one- WARRANTY half of what you'd expect to pay! - Made In The United States - SPECIFICATIONS 3 outputs: Protection built in, current limiting, with Fixed 5 VDC ± 0.2V thermal shutdown. 2 variable $1'/a V to 215 VDC Power: 108.135 VAC. can be used as pos. or neg. Polarity -floating; Dimensions: 81/4" x 31/4" x 7'/." (WxHxD) Ripple less than 10mV at full load, Wood grain finished metal case. CIRCLE 242 ON FREE INFORMATION CARD Regulation 1% no load to full load, Weight: 4 lbs., 9 ozs. Line Regulation <0.2% 108 VAC to 135 VAC. Lighted on/off power switch, easy -to -read Current: Voltmeter and large binding posts. Inexpensvie conversions kits are available Fixed supply 1.0 amp max. Warranty: one year full replacement for field installation on existing units. The total Variable supplies 0.5 amp max. warranty from date of purchase. cost of the enhanced -bandwidth conversion REPRESENTATIVE INQUIRIES INVITED kits, including installation, is expected to be DISTRIBUTOR AND under $20.00.- Midland LMR, 1690 N. Top- ping, Kansas City, MO 64120.

CORDLESS STEREO HEADPHONE sys- MiArEMI tem works with any audio source: stereo systems, TVs, and radios. It consists of a E. W. ENGINEERING, INC. transmitter and stereo headphone receiver, or transmitter and stereo receiver for use with VISA, MASTERCARD, AMEX TELEPHONE ORDERS ACCEPTED! any headphones. 6 Herman Drive, E. Granby, CT 06026 203/651-0285 The components use infrared light to transmit audio information normally carried by wire. The transmitter, IRT-200, installs easily; CIRCLE 215 ON FREE INFORMATION CARD hookup is by phone plug, and adapters are included. With both headphones and re -

13 EQUIPMENT REPORTS

moved from the base and placed under the Ungar Electronic Soldering perature is selected using the RANGE workbench or on a shelf. The system con- switch and TEMPERATURE slide control. System 9000 trol module can also be mounted under a Once he well-balanced iron with cool grip shelf or on a wall using an optional has reached the proper temperature, This soldering system lets mounting bracket. In addition, the iron you're set to go. All controls and the read- holder and the sponge tray can be posi- you set the iron out are located on the system -control tioned to accommodate either right-hand- temperature precisely module. ed or left-handed users. Calibration of the unit is done against Setting the temperature room -temperature. The procedure is done But what really sets that unit apart is the with a cold iron by turning the unit off, adjustable temperature scale. Since the placing the RANGE switch in the center idling temperature can be adjusted over a CALIBRATION position, and then turning range of 420°F to 800°F (215.5°C to the unit on. Once that's done, the ADJ 426.6°C), the user can set the idling tem- control is rotated-using a slotted screw- perature according to the requirements of driver-until the temperature readout, a specific application. The settings are disregarding the the last zero, indicates arranged in increments of 20°F over two the room temperature. That is, for a room ranges. Once set, the system will main- temperature of 70°F, the readout should

tain the temperature to within - 10°F indicate 700°F. An LED-bargraph-type display is used As you might expect, the instruction to show the actual iron temperature. That manual is really no more than a four -page type of display is used so that you can see flyer. It covers some of the features of the clearly and directly that the unit has reach- unit, and briefly goes over its installation, ed or is maintaining the selected tem- use, calibration, and maintenance. Also A LED on the display included are some pointers on the prepa- CIRCLE 244 ON FREE INFORMATION CARD perature. pulsating indicates slight variations in iron tem- ration and care of soldering -iron tips. WHETHER YOU ARE BUILDING AN ELEC- perature. There is no information regarding the the- tronics project or repairing a piece of The system control module and base ory of operation, or a schematic. A list of equipment, the most critical part of the are made of attractive black and beige user-replaceable parts, and their Ungar job is the soldering. That's because even a plastic. As is appropriate in this type of part numbers, is provided. single cold solder joint or solder bridge device, all the plastics are self-extinguish- With its list price of $190.00, the Elec- can cause a device to fail, and tracking ing to reduce any chance of a fire. Also for tronic Soldering System 9000 is ob- down the source of that failure can often safety, the system is three -wire grounded, viously not aimed at the occasional user. be next to impossible. burn -resistant cords are used, and circuit - But, if you do a lot of building or repair- Of course, the most important part of breaker protection is provided. ing, and you are serious about the work the soldering operation is the iron itself. Operation of the unit is simplicity itself. that you do, then this unit, with its com- Well, for those who need or demand the The unit is switched on using a front - bination of precision and convenience best, Ungar (Division of Eldon Indus- panel POWER switch, and the desired tem- features, is going to be hard to beat. tries, Compton, CA 90220) offers their Electronic Soldering System 9000. That Z30 unit offers a selectable -temperature preci- Regency Model sion soldering iron, a built-in iron stand, Programmable and a large capacity sponge tray. Scanner The unit is designed for maximum flexibility and convenience. The soldering station can be placed directly on a workbench using the base provided, or, if desir- Listen in on the ed, the system control module, which excitement of the houses the unit's electronics, can be re - public-service bands CIRCLE 245 ON FREE INFORMATION CARD Ungar 9000

OVERALL THERE'S A LOT OF ACTIVITY AND EXCITE - on any one or more of those frequencies at PRICE ment to be found on the VHF and UHF any time, the most effective way to listen EASE ilk. bands. Police, fire, government, mobile in is with a scanning radio. One such OF USE telephone, amateur radio, and many other radio that we recently had a chance to INSTRUCTION services use that portion of the spectrum examine is the Regency Electronics (7707 MANUAL for communications, and listening in on Records St., Indianapolis, IN 46226) PRICE communications has become a pop- model Z30 programmable scanner. VALUE those ular pastime. That unit is a programmable 30 -chan- 1 2 3 4 5 6 7 8 910 Because of the wide range of frequen- nel, three -band, FM scanner receiver. It cies we are dealing with, and because also incorporates a digital alarm clock. It Gods e some exciting activity can be taking place continued on page 20

14 Electronics Paperback Books Quality Paperbacks at Affordable Prices

Thir The BARD THE PRE- sae ice-r..a,..... SMaMM CntreMl °-°+e" .', P.v Abq Compsnirrr . the 1K COMPUTER BOOK. e $5.00. Aimed at the - -- absolute beginner with co knowledge of corn- 1t "' 4k pulars. Anon -technical 3 s+`e - j1Tj -_..t_-. discussion that helps t Ny -`"R - you enter the computer t world painlessly, Pt fw ni , , d. x[; IC Prtsecte ..- Protect_,M"'''' easel P/I]Ote for ae9innera i..... Meertale ,,.«Cffleeer 6itlr ..., ... SatyrSailr 0 Moelle 01!14SI T-r" 4f4 'Into514ads.etlonro Yktae AN INTROOUC- r- .t 1.11111111fQ,-t TION TO VIDEO. -." It ,.. 55.00. Perfect for Me Y ,,,tea 4 VICR. tf' : 1.4.pp r..,. buY a Discusses G 4,,a 4á(1r V Pros & Cons of the van -^n ' S--- - iº rJ jpti bus formats; vide J re »<. .e- ._ discs; videotext. tape A copying and more. L.._ i

30 SOLDERLESS MODERN -AMP - OP ART OF PRO- ART OF PRO- POWER SUPPLY ELECTRONIC BREADBOARD PRO- PROJECTS. $5.00. CRAMMING THE 16K CRAMMING THE 1K PROJECTS. $4.50. PROJECTS USING JECTS BOOK-1. Wide range of special- 2X81, Topics 06.25. in- 2X81. $5.00. How to Contains designs and SOLAR CELLS. $5.00. 85.75. Whenever possi- Ized op circuits in- -amp dude lull screen, scroll- use the features of the construction details for Simple circuits that Sie Me same pans are eluding lo -noose, lo- ing, PEEK & POKE, 2Xa1 in programs that almost any power sup- have numerous so- used in several pro- distortion, ultra -hi input plus actual working tit the 1K machine and ply the experimenter is plications around the jects, Even a first-time impedance. etc. programs. are still fun to use. likely to need, home. builder can complete BASIC &PASCAL. 0 these circuits. MULTI-CIRCUIT 54.00. Takes BASIC & C REMOTE CON- ELECTRONIC TIM - BOARD PROJECTS. PANION. $5.00. Writ- Pascal and develops CRAMMING TECH- / I 55.00, Radio-control TimingLees for YOUR ELECTRONIC projects that can all be assembly language guages simultaneously. MOUES, $5.00. Based Infrared, visible light, & almost any application PROJECTS WORK- Wilt on a single programmer. A discus- on author's own experi- ultrasonic systems are the expenmenter might ING. $5.00. Helps you printed -circuit board. All soon of features 6809 & ere in learning BASIC all Included, along with need. A most valuable troubleshoot end repair are powered by a 9V reference work for the and helping others to methods of applying reference. Tame -Wilt projects of battery. 6809 programmer. team to program. them. every description. IC PROJECTS PRACTICAL ] COM- ] A MICROPROCES- D FIRST BOOK OF 7 ELECTRONICS ELECTRONIC COUNTER DRIVER MINI-MATRIX FOR BEGINNERS. PUTER EX- SOR PRIMER. SIMPLIFIED CRYSTAL $4.50. TRANSISTOR EQUIV- TEST EQUIPMENT & NUMERICAL - BOARD PROJECTS. $5.00. Inexpensive digi- PERIMENTS. Painless $4.50. approach to ALENTS. & SUB- SET CONSTRUCTION. CONSTRUCTION. DISPLAY PROJECTS. $5.00. A variety of pro- tal anc linear IC's are Fills in background to computing $4.50. for the be- STRUTES. $3.75. $4.50. Construction de- $4.50. Features selects that can all be used to assemble this microprocessor by con- ginner. Step-by-step tails of a wide range of plcations & projects built upon a mini -matrix selection of circuits in. strutting typical compu- explains computer op- PRACTICAL COM- 7 ELECTRONIC test equipment the ex- using various types of board that has 10 strips tender for the be- ter Circuits using dis- orations and assembly. PUTER EX- HOUSEHOLD PRO- perimenter can build at numericabdisplay de. and is 24 holes long, ginner crate logic components. PERIMENTS. $4.50. JECTS. $4.50. home. vices,

hrM. YtlawY tornotbMr Stations 1 a .. Mdb th Mowers Lkrraenb Glom* Ta shoos Guide ' Myltordcs +#OepágKPt of Elewtoaux ace tleiaa Grade TRONIC BUILDING ..r - .mae (,A J BLOCKS-Book 1. __ .._ 55.00. All eleconcs ,.... Y circuits consist sim- ^{ ple building books. paertat F'i When you know how to et Ntatalm et Ettenronan 1111111 make the blocks you l - :., can easily create your 4 J5 Electronic own projects. r s w I/I w.,. -e...., Colette 4. NnMbod, E- M1 arewy An tfen 1 se ri __.. cc'ritlilSet Radio

B4 -y-c jayri PRACTICAL ELEC -LI . ,. t TRONIC BUILDING °: :,i: ..i BLOCKS-Book 2. 'r.' L 1 i $5.00. Circuits that pro- ,.. THE SIMPLE SEMICONDUCTOR tees signals. Combines ELECTRONIC CIR- TECHNOLOGY. $5.75. PRACTICAL ELEC- HOW [ TO MAKE with those in Book 1 CUIT & COM- Everything you always TRONICS CALCULA- WALKIE TALKIES. PONENTS. $5.75. All needed to know about TIONS AND FORMO- 55.00. Describes equip- the fundamental theory solid-state devices in LAE. $7.50. A basic ment for low -power ; ANTENNA PRO- CB PROJECTS. needed to lead to a full one volume, reference work that handheld operation. JECTS, $5.00. Covers $5.00. A number of understanding of the bridges the gapa be. 112 ACTCIAL ELECT Book 1 & Book 2 g ppages g of must practical antenna de- useful sand interesting simple electronic s. COMMUNICATIONS. Iween PRACTICAL ELECTRONIC BUILDING BLOCKS. comDlory reading for the tledi- signs including active. designs for CB and Its components. $7.50. Covers most technical 09,00. Shipping Included. Save 51.75. theory & cut cared expenmenter loop &ferrite types that accessories. Speech modern communication and tried methods. are easy & inexpensive processor, interference C ALTERNATING systems. Line. micro - ELECTRONIC to build. INTERNATIONAL 7 filter & more. CURRENT THEORY. wave. submarine, sat- CALCULATOR US- -- EQUIVALENTS ELECTRONIC $5.75. Alternating cur- elide, digital multiplex, ERS HANDBOOK. HOUSEHOLD PRO- RADIO STATIONS CRYSTAL SET rent theory without radio & telegraphy. GUIDE.DIO QUIV5.75. Helps 53.95. Presents forma- E JECTS. 54.50. GUIDE. $4.75. C0m- CONSTRUCTION. which there you lind substitutes for CONTROL can be no tae data. methods of RADIO prehensive listing of $4.50. Packed full Me many different FOR BEGINNERS. of comprehension of FIRST BOOK OF calculation, conversion ELECTRONIC transmitters around the easy too plicate de- speech, music, radio. typas of semiconductor $4.50. HI-FI SPEAKER EN - factors & more from the MUSIC PROJECTS. world. Presents loca- signs for crystal radio or Television. diodes in use today. CLOSURES. 54.50. view of the calculator $4.50. Lion, frequency. power. receivers. r ELECTRONIC '-I INTERNATIONAL GAMES $4.50. LONG DISTANCE AN TRANSISTOR EOUIV- POPULAR ELEC- ^i INTRODUC- SOLIDCIRCUITS.RCE LINEAR IC EQUIV- TV RECEPTION TION TO RADIO DX- MICROPROCESS- ALENTS GUIDE. TRONIC PROJECTS. NOVELTY ALENTS AND PIN SINGLE IC PRO- FOR THE EN- ING. $5.00. Listen, in ING SYSTEM & CIR- $7.50. Products of $3.50. CONNECTIONS. JECTS. $4,25. x'75' THUSIAST. home. s A than 100 man- $5.00.CUITS.morebroad- Shows equivalents & pin Practical & au- casts originating comprehensive guide ulactureß are listed & $ß.25.yourtPROJECTS thorsetive connections of a Popular introduction thousands of miles to all of elements of 28 TESTED - cross-referenced with RADIO CIRCUITS OPTO -ELECTRONICS. TRAN user ICs,tetl seleCtbn of to this unusual aspect away. Tells how you a microprocessing SISTOR PROJECTS. possible replacements. USING IC'S. $4.50. 55.00. linear ICs. of electronics. can do d system. $4,25,

ELECTRONIC TECHNOLOGY TODAY INC. AN5 P.O. Box 240, MassapequaIN Park, NY 11762

Number of books ordered Name

Total Price of Books $ Address Sales Tax (NY State Residents) Shipping (750 1st two books, 30¢ ea additional) City State 71P TOTAL ENCLOSED $ II J Ludio- lecironis,.. i,,,,. SPECIAL REPRINT BUILD A BACKYARD SATELLITE TV RECEIVER

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Send away today for your 36 -page home constructor, can meet them. proaches to making one that will booklet containing a complete reprint Find out what mechanical and elec- work for you. of all seven articles in 'he series on tronics skills you need. RECEIVER -SYSTEM hardware, and Backyard Satellite TV Receivers by RECEIVER CHARACTERISTICS, how it goes together to bring you di- Robert B. Cooper Jr. technical details and specifications, rect -from -satellite TV reception in along with examples of actual re- your own home. This all-inclusive report gives you all ceivers built at comparatively low the data yoJ need to build your own cost. To order your copy: Backyard Satellite TV Receiver. ANTENNA DESIGN... and ex- Complete coupon and enclose it with actly how you can build a spherical your check or money order for $7.00. TELLS ALL AIBOUT domestic satel- antenna, while keeping total earth - plus $1.00 for postage and handling. lite communications, with full details station cost for the complete system We will ship your reprint within 6 on how you can pull those elusive TV under $1,000. weeks of receipt of your order. All signals from space. THE FRONT END is critical when others add $4.00 for postage. New IN LEGAL REQUIREMENTS, techni- you build your own system. We help York State residents must add 58c cal specifications, and how you, the you explore several different ap- sales tax.

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16 ONLY NRI GIVES YOU ÌUFAL COMPUTER SYSTEM TRAINING Built-in monitor More practical experience as you Your hands-on training displays up to 80 install double -density floppy takes you inside your characters for easy disk drive. Software includes TRS-80 Model 4 word processing TRSDOS°, DOSPLUS®, machine computer to install and spread sheet language monitor, and two game integrated circuits and programs. programs. Electronics comes to enlarge memory to 64K. life on your NRI Discovery l.ab®.

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Working with it, your goal. how to work on computer systems. you'll get practical experience in add- Only NRI includes a complete system ing peripherals, learn maintenance Free Catalog Tells Much More.. . with your training...total training that and servicing operations. And you'll Send Today gives you hands-on experience with use it for hard copies of important See all the interactive training computers, peripherals, and software. programs, business records, and equipment you get in this state-of-the-art Training that builds /he knowledge, word processing. course in today's technology. Look over skill and confidence you need to the lesson outlines and descriptions of become a computer professional. Understanding Built On Experience the exciting experiments you'll perform. You start with the basics, rapidly And look at other high-tech career fields Get Inside the Famous TRS-80 build on the fundamentals of elec- like Robotics, TV/Video/Audio Servicing Model 4 Computer tronics with bite -size lessons to and Data Communications. Learn programming techniques master advanced concepts like digital Mail the postage -paid card today for troubleshooting . .. go inside to logic, microprocessors, and com- to see how NRI can give you the skills expand its RAM to a powerful 64K.. . puter memories. and confidence you need to start a even install a double density floppy You'll reinforce this new under- good -paying career as a microcom- disc drive. standing with hands-on, practical puter technician. If the card has been You'll become familiar with demonstrations and experiments that used, please write. computer languages...BASIC, the give you real -world experience and most popular microcomputer pro- build almost intuitive skills. You'll use gramming language, and machine the exclusive NRI Discovery Lab° to AiPfCHOOLS language for diagnosis and repair see what makes transistors tick, build McGraw-Hill Continuing work. You'll run software that and test working electronic circuits Education Center demonstrates computer operation, that duplicate key computer circuitry, even learn to do your own program- construct digital logic circuits that 3939 Wisconsin Avenue, N.W. Washington, DC 20016 ming. You'll become proficient at demonstrate computer performance. rerrie modifying programs to fit your And, you'll probe into the very heart of We'll give you tomorrow. 1:1111 business or family computing needs. your computer using the Discovery îes-go is a trademark of the Radio Shack division of Tandy Corp.) using a front -panel keypad called the Pro- Z30 EQUIPMENT REPORTS Regency gram Panel. (As you would expect in a continued 14 unit of this type, except for OVERALL from page the one used as PRICE a reference, there are no crystals. Instead, EASE a microprocessor-controlled frequency OF USE can be powered from either the 117 -volt synthesizer is used.) INSTRUCTION line or from a 12 -volt negative -ground DC The keys on the Program Panel are MANUAL supply such as found in a car, truck, or grouped into two types: the mode keys and PRICE boat. To simplify mobile installation, a the program keys. The mode keys are / VALUE DC power cord is included. Also included used to place the unit in one of its various 1 2 3 4 5 6 7 8 9110 is a detachable telescopic antenna. modes. They are also used to activate or The unit is compact, measuring 103/4 x deactivate the unit's special features and 90° i0 c,0°_,,>'''(? 27/8 x 83/8 inches, and weighs 23/4 pounds. to control the built-in alarm clock. The It is housed in a brown plastic case, with a program keys are used for entering fre- trolled using the DISPLAY DIM key. simulated wood -grain finish. quencies and for selecting the channel The unit has three primary modes of Turning to the receiver itself, it is a number during programming. operation: search, scan, and manual. The double -conversion, superheterodyne cir- Frequencies, channel numbers, and the search mode is used to find new frequen- cuit. It receives narrow-band FM com- time of day during periods that the unit is cies. To use that mode, the PROGRAM key munications over three bands: 30-50, turned off, are displayed on a blue vac- is pressed and upper and lower search 144-174, and 440-512 MHz. The unit uum -fluorescent readout. In addition, the limits are entered. Once that is done, the boasts a sensitivity that varies by frequen- readout can display a variety of prompting search is initiated by pressing the SEARCH cy from 0.7 to 1.5 µV (12 dB Sinad, messages to alert the user to a particular key. The band of frequencies selected is maximum), and a selectivity of ± 7.5 kHz condition. For instance, if the frequency then searched continuously in 5 -kHz at 6 dB and ± 18 kHz at 50 dB. entered is not within one of the bands that (VHF) or 12 -kHz (UHF) increments. the unit covers, a FR ERR message is dis- Once you have found a frequency of Use played. Also, a variety of annunciators are interest, it can be entered into the unit by Aside from an ON/OFF switch and used to alert the user to which special placing it into the manual mode. Entering VOLUME and SQUELCH slide controls, all functions and features are active. Finally, frequencies is a very simple operation. It functions and frequencies are entered the brightness of the display can be con - involves merely pressing the MANUAL key, entering the frequency using the program keys, pressing the ENTER key, and

finally entering the channel (from 1 to 30) that you want the frequency stored in. After you have programmed the fre- WHY SPEND A FORTUNE ON A Now we can quencies of your choice, they can be scan- DIGITAL CAPACITANCE detect a breast ned automatically by using the scan cancer smaller mode. That mode is entered by pressing METER? than this dot. the SCAN key. The MC100A comes completely assembl- The Z30 has several special functions ed and calibrated and at $79.95 is an that are designed to give the unit max- outstanding value. The extensive range of 1 pF to 9,999 uF (no external meters re- imum flexibility. In the scan mode, you quired) and true hand held portable size may want to delay the resumption of scan- (only 42/," x 21/2" x 1'/2") make the MC100A an extremely practical and easy ning after activity on a channel has ended to use instrument for the hobbyist technician or engineer. so that you might hear a reply that might CHECK THESE OTHER FEATURES otherwise be missed. Pressing the DELAY 'Basic accuracy 1% (± one count) on key causes the unit to pause for about 2 pF, nF ranges, 3"/ (± one count) on uF range. seconds before resuming the scan. In the 'Uses single 9V battery (not included). 'Decimal points light up when battery is At such an early stage, search mode, the DELAY key is used to low or when capacitor is overrange. your chances of living a select between a 4 -second delay and a 'Full 4 digit high efficiency LED display long, healthy life are ex- uses special circuitry to save on batteries. hold function. If the hold function is se- cellent. But we need 'Constructed with a tough impact resis- lected, the unit will remain on a pre- tant plastic case. your help. The only viously active frequency until either the proven way to detect a ONE YEAR PARTS S. SEARCH Of DELAY key is pressed. (Note cancer this small is with LABOUR WARRANTY DELAY a mammogram. A mam- that pressing the deactivates the 1pFta9,999 uF mogram is a low-radia- hold function.) DAETRON special functions include a pri- SUITE 105 tion x-ray of the breast Other 1748 MAIN STREET capable of detecting a ority mode that lets you sample a favorite BUFFALO, N.Y. 14211 cancer long before a frequency every two seconds during the (416) 255-9701 X79.95 DEALER ENQUIRIES INVITED lump can be felt. If scanning process. Channel 1 has been set you're over 50, a mam- PLEASE SEND ME aside for that function. A channel -lock- mogram is recommend- (Quantity) MCtOOA(s) ® $79.95 U.S. $ out feature lets you force the scanner to ed every year. If you're SHIPPING AND HANDLING $2.75 (per instrument) skip over any channel that you select. between 40 and 50, or I ENCLOSE CHECK D MONEY ORDER BILL MY VISA TOTALS The manual that accompanies the unit VISA CARD NO. have a family history of is, as you would expect, pretty much just EXPIRY DATE SIGNATURE breast cancer, consult an It covers the opera- Immediate shipping on orders with money orders or VISA. your doctor. In addition, instruction manual. Personal checks please allow 2 to 3 weeks for clearance. of course, continue your tion of the unit in step-by-step fashion, but NAME regular self -examina ADDRESS has little in the way of technical details CITY STATE ZIP CODE tions. such as theory of operation, schematics, parts lists, or parts -placement diagrams. CIRCLE 210 ON FREE INFORMATION CARD Anterlcan tancer Society continued on page 127

20 Electronics

MARC STERN and Photography

Picture taking-and all WHILE MANY CAMERAS ON THE MARKET TODAY LOOK MUCH areas of the same as cameras some 25 years ago, they are hardly in photography-have the same class. Cameras today are "smart." All a photographer has to do is bring the camera up to his eye and benefited from the press the shutter release. No longer does he have to worry introduction of about whether a scene is too bright or too dark. Photosen- electronics into the sors take care of reading the brightness of a scene, setting equipment used. In this the exposure, and even activating strobe circuits if extra special section we'll light is needed. examine some recent Some cameras on the market even save the photographer from worrying about focusing. Instead, using advances in this area. sonar or one of several infrared rangefinding-techniques, they determine the camera -to -subject distance and cause the lens to be focused for the photographer in a fraction of a second. There are cameras available from Kodak, Polar -

21 oid, and other companies that have this feature. All these cameras allow the photographer what is known as "decision -free" photography, freeing him to be creative. In other words, it's point -and -shoot photography, just as in the days of the box Brownie, but now the cameras are far more sophisticated and the results are much better. In fact, the whole picture -taking process is far simpler, because "decision -free" photography also extends into the realm of accessories. There are now light meters on the market that do virtually all the thinking for the photographer. He no longer has to spin dials or match needles; instead, a liquid -crystal display gives him all the information he needs. It's much the same with strobe units, too. Instead of letting the photographer worry about distances, lens openings, and other factors that can affect a flash exposure, dedicated strobe units communicate directly with the camera, presenting exposure information through the accessory "hot shoe." The camera's logic circuitry handles the input from the strobe and sets the correct exposure. If a strobe is not designed to connect directly to the camera, it will present its information on an LCD display so the photographer just has to dial it in. Further, using photosensors, the strobe will determine when it has delivered enough light, and then shut itself off. "Decision -free" photography even extends to the darkroom, Although cameras are getting more and more complex, the electronics where the photographer will find microprocessor -driven enlarg- they contain make them easier to use than ever. ers that remember correct exposure settings. There are also digital color -analyzers that interface with enlargers and set the correct color -filter combinations. That leaves the photographer free to create. (For the photographer who likes more control of devices-are small enough to fit in a photographer's shirt pock- things, there are still manual adjustments that can override the et. If large -scale -integration techniques hadn't been used, that settings determined by the microprocessor.) would have been impossible. How we got here All -electronic photography To be fair, some cameras were fairly automated a few years And, while changes have been taking place in camera and ago, but they still required a great deal of work on the part of the photographic accessories, the photographic medium, too, is photographer. For example, light meters have been an integral changing. While recent developments have improved film qual- part of cameras for years. However, they have usually required ity while reducing the amount of silver used in making that the photographer to handle either setting the aperture or shutter material, silver is still expensive, and not getting any less so. speed, or both, himself. In the late 1960's, an advanced camera It's possible, though, that in the near future the photographer might have had a match -needle system that determined the won't even need silver-halide -based film. Instead, totally elec- correct exposure. The photographer had to change aperture or tronic photography will take its place. The concept has been shutter speed settings until the needle was centered. The needle admirably demonstrated in Sony Corp.'s Mavica photographic was electrically actuated, but mechanically linked to the cam- system. era's aperture- and speed -setting mechanisms. Borrowing heavily from video and recording technology- Autofocus, too, was available some years ago, but the appara- and creating quite a bit of its own-Sony has developed a tus using it was large and clumsy. completely film -free system. Its Mavica camera, a marvel of What has changed the picture? Integrated circuits. If a camera electronic technology, is very little larger than the standard or accessory manufacturer had tried to make today's type of 35mm film camera with which we are all familiar. But, while it camera 10 or 15 years ago, it probably would have been as large looks normal enough on the outside, things are very different as the photographer himself. However, as circuit -integration inside. It still uses a lens, but rather than focusing the photo- technology headed from small scale through medium- and large- graphic image on the film plane, the image is focused on a scale and up to very -large-scale, more and more components solid-state high resolution charge -coupled device. The resulting could be squeezed into a single device. Today, for instance, electrical signal is then processed and recorded on a miniature camera manufacturers are relying on 42 -pin and 48 -pin flat -pack floppy disk, a miniature version of the sort used by computers. type integrated circuits to perform the information processing The images stored on the disk can be viewed on a TV screen they need. Those circuits accept information about film and when the disk is inserted into a special player; as is the case with lighting conditions and their preprogrammed logic determines videotape, the pictures can be viewed instantly. Yes, it's true what actions to take. that you can get instant pictures from Polaroid or Kodak cam- For example, imagine that a photodiode positioned in the eras, but you have to keep buying film for them; the Mavica's camera's viewfinder finds that the light level is too low for "film" can be reused. available -light photography. It therefore sends a message to the If you decide you want to save a special photo for the family master logic -circuitry that indicates a low -light situation. The album, the Mavica system includes a printer that can make a logic circuitry, after receiving the message, activates the driver color print on ordinary paper in five minutes. You can even send circuitry for the electronic flash, and the strobe fires auto- a Mavica picture by telephone; imagine how that could speed up matically when the shutter release is pushed. Thus, the photo- news reporting! grapher never has to think about when to use the strobe because Because the Mavica system is all -electronic, it may be possi- the camera makes the decision for him. That's just one example ble in the future to integrate Mavica photos with microcomputer of what goes on inside the body of a modern camera. technology and write letters with your word processor that Imagine trying to do that with the discrete componentry of 10 include pictures for Grandma. or 15 years ago. The camera would have been enormous! Yet, as These are only a few of the ways that electronics is affecting a look in any photo store or catalogue will tell you, many the world of photography. For a fuller description of what's automatic cameras-some of them sophisticated 35mm happening, please continue reading. R -E Sony has developed a The all -electronic photographic system that does away with film completely. To do so, its engi- MAVICA neers had to create an entirely new technology.

.ab

MARC STERN

FOR NEARLY 160 YEARS, SINCE THE DAY NICEPHORE NIEPCE needs on the spot. In that way, party -goers can have instant exposed a piece of silver-bromide -coated glass to the sunlight souvenirs of their party. and ended up with a picture of his yard, we have relied on Let's look at the basic Mavica system, beginning with the silver -based materials for photography. camera. With the shortages of the last few years, we have begun to realize that natural resources are finite and will one day run out. The Mavica camera Silver is one of those natural resources, and as it has become Figure 1 shows the Mavica camera. About the same size as a increasingly harder to find and process, its price has increased. conventional 35mm camera, about the only thing the Mavica has That has resulted in a corresponding increase in the cost of in common with one is its optics. Inside, they are as different as silver -based products, including those used for photography, day is from night. and has led photographic researchers to search for new ways of Instead of using a roll of film, the Sony camera uses a taking snapshots. Mavipak recording disk-constructed much like the floppy One of the avenues into which they have turned is electronics, disks used by microcomputers-to store pictures. The image and the result is in all -electronic still -photo system from Sony produced by the lens is focused onto the face of an integrated Corporation (Sony Drive, Park Ridge, NJ 07656) called the circuit called a CCD (Charge -Coupled Device), which couverts Mavica System. it into electrical energy. That energy is converted into a signal Mavica stands for MAgnetic Vldeo CAmera, and it combines that can be recorded on the magnetic disk, which is capable of electronics and electromagnetic technology into a non -silver - holding 50 pictures. based photographic system. First introduced two years ago, The Mavica acts much like a video -recording system. It uses though not yet marketed, it represents a potential giant step in the same general principles but, instead of using a vacuum tube the history of still photography. Imagine a press photographer in for image conversion, it uses a CCD. Most video terminology the field hurrying a photo disk, not to a lab, but to a telephone, can be applied to it. and almost instantly sending his pictures back to a newspaper or The CCD is an 11 x 12.1 -nun integrated -circuit chip with an wire service. image area of 6.6 x 8.8 mm. It is the heart of the Mavica Or, how about an amateur photographer taking pictures of a system. birthday party? Instead of having to send the his film out for The resolution of the CCD is high-the image formed by it photofinishing, he can load the results of his work into a Mavi- consists of an array of 570 x 488 pixels (a pixel is a picture pak viewer for instant viewing on a home television -set, and can element). The signal generated on the image area is sent to a then use a Mavigraph printer to produce as many prints as he storage area on the chip during the vertical blanking -interval. In J.

SHUTTER VIDEO BOARD The Mavipak is inserted into a disk -drive unit that revolves at VIEW FINDER RELEASE a speed of 60 revolutions -per -second. A compact motor that is FUNCTION SWITCH SELF TIMER controlled by servo -circuitry ensures that the speed remains CAMERA constant. BOARD One would think that due to the high speed of the disk's rotation, there would be some stability problems, but Sony claims otherwise. Because of its small size, the disk is only Any MIRROR minimally affected by aerodynamics or centrifugal force. tendency for the video disk to move away from the recording head is limited by a guide plate. Instead, because of the position of the guide plate, an air cushion is formed that helps keep the disk -to -recording head relationship constant at 0.07 micromet- BATTERIES ers as shown in Fig. 3.

GUIDE PLATE ,JACKET

MAVIPAK DISK AIR DISK DRIVE CCD LENS

FIG. 1-THE MAVICA CAMERA is about the size of a large 35mm camera but has little in common with it save for its shape and optical system-it is entirely electronic.

RECORD HEAD DISK response to a clock pulse, the image is then read out of the FIG. 3-A SPECIALLY DESIGNED GUIDE PLATE uses air pressure to keep storage area into a readout register after the vertical blanking - the Mavipak disk in contact with the record head. interval. Color filtering is handled by a filter with red, green, and cyan stripes. The Mavica's CCD was designed to take advantage of the Since that arrangement ensures stability, there is no need to "narrow -channel" effect-when the width of a MOS transistor have other pressure exerted to bring the head and disk together, electrode is narrowed to about 2 micrometers (µm), a change in and that, in turn, ensures a considerably longer working life for electric potential can be produced across it if it is excited by the recording disk. light. The small size of the channels means that the CCD can Head -to -track alignment is also very important, and is a must have simple, densely packed, image -sensing cells. The unfor quality picture -reproduction. If the head and track being complicated geometry also means that the driving circuitry can recorded or read are not within ± 10 µm of one another (a lateral be reduced to simple two-phase clocks, and that the power measurement), the signal-to-noise ratio becomes too high and requirements are low. quality deteriorates. However, Sony admits in published papers With the light falling directly on the CCD unit, its spectral that that figure is hard to achieve (it has been found that tempera- response (sensitivity to a wide range of colors) is high. To ture variations alone can cause the figure to vary by as much as counteract "blooming" (image degradation caused by excess ± 30 µm) and has been accommodated for by tracking -error - electrons spilling from one sensor cell to its neighbors), an correction circuitry incorporated within the playback unit. overflow drain was added to the chip; Sony claims that the drain Like a computer's floppy disk, the Mavica's recording causes only an insignificant reduction of sensitivity. medium is a circular sheet of thick plastic film, coated with a magnetic material. It is housed in a plastic jacket measuring The Mavica disk about 2'/s x 21/4 x 1/4 inches, and the entire assembly weighs In the standard photographic process, the storage medium is only eight grams (a little over '/a ounce). silver-halide -coated film. The film captures the image, and is Because the magnetic Mavipak disk is erasable, it can be used later developed to make the latent image visible. However, in over and over again. the Mavica system, images are recorded on a magnetic -material - The first image is recorded on the outermost track of the disk, coated disk, the Mavipak (see Fig. 2), which is inserted into the with subsequent images recorded on tracks closer and closer to camera. its center. To keep the size of the disk small, Sony engineers had to develop a high -density recording method. To obtain the best possible magnetic characteristics, the development team turned to a ferromagnetic metal alloy-similar to that used in high - quality audio cassettes-rather than using a metal -oxide powder. That coating meant an 8 -dB improvement in output level, and permitted the use of a disk half the size of a metal oxide one. However, that development is only half the picture. To achieve true high -density recording, the surface of the disk must be extremely smooth. Smoothness helps limit modulation noise and the losses resulting from the short wavelengths used for recording. The Mavipak disk is able to boast a 0.05 -micrometer peak -to -peak smoothness. The magnetic characteristics of the disk are extremely even-output level along a track varies by no more than ± I dB. The result of Sony's efforts is a disk that can record wavelengths of 0.8 µm-equivalent to signals with a frequency of 3.75 MHz. Signal processing FIG. 2-THE MAVIPAK DISK measures only about two -inches square, yet The concepts embodied in the Mavipak system go a long way can store 50 pictures. toward ensuring that picture quality will be good. But there are other necessities, Sony has found. To produce high -quality, reproducible images, it is necessary to have luminance and chrominance signals with good resolu- PRINTING PAPER PLATEN tion and a good signal-to-noise ratio. Accomplishing that is not easy because, due to the limited space available within the Mavica, the circuitry cannot be too complex. To keep things simple, the Mavica uses a single-track, line - sequential recording system; instead of being recorded sim- PAPER -LOCK ultaneously, the R -G and B -G signals are mixed separately with MECHANISM the luminance -plus -sync signal, and recorded one after the other. That, Sony admits in published technical papers, causes DYE SHEET some deterioration in the vertical resolution of the chrominance signal. But, while the amount of deterioration is on the order of 50 percent, it is not noticeable because the horizontal resolution, determined by the one -MHz bandwidth of the chrominance signal, is still less than the vertical resolution. Other single-track recording methods were dismissed because of potential jitter THERMAL HEAD FIG. 5-IN THE PRINTING PROCESS the paper. wrapped around a platen. problems that would have led to hue fluctuations. is brought into contact with a series of dye sheets and the thermal ele- The recording circuitry is pretty straightforward. When a ments that transfer the dye to it. photographer using a Mavica camera captures a scene, the image of that scene is converted by the CCD into an analog electrical signal. That signal is then broken down into four and maintaining the playback head in that position. components-luminance, red, green and cyan-by sample and Each track on a Mavipak disk contains one picture consisting hold circuits. The green and cyan circuits are used to produce the of 262.5 video lines. That's the equivalent of one video field; blue signal and all of them are then fed to processing amplifiers. two fields make up a complete video frame of 525 lines. Because The processing amplifiers output the processed luminance, the Mavica pictures are still pictures, each track is played over red, green, and blue signals, with the luminance signal then and over as the picture is viewed. To generate a standard full - being added to the sync signal and fed to a frequency modulator. frame NTSC video signal, several sets of delay lines are used in The red, green, and blue signals take a path through a matrix the player. One set takes the line -sequential chrominance in- circuit and are then converted to color -difference (R -G and formation and restores it to NTSC format; one'/;.3-µs delay line B - G) signals. From that point, the signals are selected line - and two 63.5-µs delay lines are used for that purpose. sequentially and are then fed to a second frequency modulator. To generate a 525 -line picture, every other field is synthesized The two signals are passed through low- and high-pass filters from the information contained in the 262.5 -line recorded to narrow their bandwidth and are then fed to the recording fields. amplifier. It is that final signal that is recorded on the disk. The horizontal resolution (the resolution in the horizontal Those functions are handled by specially developed LSI IC's direction-not the number of horizontal scan -lines) of the Mavi- and hybrid modules. ca picture is 240 lines; that figure is due primarily to the number of picture cells on the CCD imaging element. The recording The Mavica player capability of the Mavica disk is approximately 350 lines (hori- The final part of the basic Mavica system is the playback unit, zontal resolution), which means that we may see a considerable which converts the signals recorded on the disk into a picture improvement in picture quality in the future. that can be viewed on a television receiver. The playback head of the player is analagous to the record head in the Mavica The Mavica printer camera. However, while the record head can only move from Although the Mavica system represents a breakthrough in track to track from the outside toward the center of the disk, the ' `filmless` ` photography, it would be of little value if it were playback head can move from one track to another in either limited only to viewing photos on a television receiver or moni- direction; that allows pictures to be accessed at random. tor. Recognizing that, Sony has also developed the thermal color As was mentioned earlier, the tracking error induced in the video printer shown in Fig. 4. Mavica camera can be sizeable. The microprocessor -controlled It is capable of taking the color output -signals from the tracking -error -correction circuitry incorporated in the player Mavica-or any other color -video system-and turning those works by sensing where the RF signal is strongest on the disk signals into color prints. It can accept either composite -video or RGB (Red -Green -Blue) signals. The Mavigraph, as the printer is called, uses a thermal dye - transfer system. As shown in Fig. 5, a sheet of paper-which can be ordinary writing paper, although a special polyester - coated type gives better results-is wound over a platen. A thermal printing -head is pressed against the platen so the paper and a sheet of material containing dye come into contact with each other. As the platen and the printing paper turn together, the dye sheet is drawn at the same speed over the printing head. The intensity of the heat produced by the print head-which determines how much dye will be evaporated and transfered to the paper-is controlled by the level of the video signal. Four colors are used in the printing process: yellow, magenta, cyan, and black (these are the same colors used to print the covers and color pages of this magazine); they are the printing equivalents of the video signal's blue, green, red, and black, respectively. Each color is contained on a separate dye -sheet, and the colors are transfered sequentially, in the order indicated above. First, the entire yellow portion of the print is produced. Then the platen carrying the paper returns to its original starting FIG. 4-THE MAVIGRAPH PRINTER can produce a color print from the Mavica or other still -video source in about five minutes. position and the magenta portion of the print is laid down...and 25 PU LSE- HEAD - COLOR -SELECT SWITCH AiD WI0TH DRIVE (FRAME SEQUENTIAL) CONVERTER MODULATION AMP COMPOSITE - VIDEO SIGNAL -o

COLOR COLOR ENHANCE COLOR DENSITY VERTICAL RAM THERMAL DECODE INVERT BALANCE ADJUST SAMPLING ONE -LINE PRINT - MEMORY B YELLOW HEAD

G MAGENTA R CYAN Y -a BLACK FIG. 6-TO MAKE A MAVIGRAPH PRINT, the video chrominance (blue, green, and red) and luminance signals are inverted to produce their opposites-yellow, magenta, cyan, and black.

so forth. For black -and -white prints, only the black dye -sheet is Photos by phone used. The flow of the printing process is illustrated in Fig. 6. In Settling on transmission using amplitude modulation, the some versions of the printer, the dyes are contained, one after Sony engineers designed a system (the receiving end of which is another, on a single piece of material wound into a roll. The illustrated in Fig. 7) that links a transmitting unit and a receiving finished print is laminated in plastic both for protection and to unit via phone circuits. The system also includes memory enhance the image. storage -devices because of the transmission -time constraints The printer scans the video image vertically-from top to imposed upon it by the phone system. bottom across the scan lines-rather than horizontally (along the It takes about 63 µs to display one horizontal line on a TV scan lines) as you might expect, and the picture is reproduced on screen. However, because of the telephone system's limited paper from left to right. It takes about five minutes for a com- bandwidth, it takes about 400 ms for the information contained plete print to be produced. by that same line to be transmitted over a telephone line. That The thermal print head used in the Mavigraph contains a row means that some sort of memory buffer must be used to store and of 512 elements-four per millimeter-to produce a picture transmit each line as the system can handle it. A similar situation measuring 43/4 x 61/4 inches. The compactness of the print head holds at the receiving end, except that the entire picture is is due to 16 special IC's, each of which contains a 32 -bit captured in the receiver's buffer. As each line is received, it is shift/store register and 32 drivers. read out, along with the lines that have already preceded it into The Mavigraph can be used to produce any number of color the buffer, and becomes part of an image displayed on the prints of a still picture taken by a Mavica or a video camera, or of receiving television set's screen via high-speed video processing a single frame or field of an image displayed by any video circuitry. device, including a television receiver, computer, or VTR. Since the system uses voice -grade telephone lines, the analog A home -video camera can be used to convert existing color signal transmitted must be able to fit within the restrictions they film negatives or positives into video signals suitable for impose. The engineering team looked at the various means of reproduction by the Mavigraph. The fact that the amounts of modulation-amplitude, frequency, and amplitude-phase-and red, green, and blue in the print can be controlled allows the decided to use double-sideband AM for reliablility. Mavigraph user to adjust the color balance of his prints to his The engineers also had to keep the system's maximum band- taste, and to experiment with unusual color -effects. Sony ex- width in mind when defining their parameters. Using a max- pects to open an entirely new market for the combined use of imum range of 300 Hz to 3400 Hz as boundaries, Sony's conventional photography and electronic Mavigraphy. engineers chose an 800 -Hz image frequency and a 1500 -Hz This printer and the system it supports have been termed a carrier frequency for best transmission quality, recognizing not new era in video technology that adds a new dimension to video. only the limitations imposed by the phone system, but also the For instance, the system can be used to produce hard color - potential for fluctuations in level, for line noise, and for system copies from signals received from teletext or videotex systems. leakage. It can also be used as an image printer for an x-ray machine, The video output of the Mavica is sampled at a rate of about 14 CAT scanner, or other medical equipment. It can even serve as a MHz and digitized. The digital information is read into memory terminal printer for office computers and as a color facsimile and is then read out at a much slower rate-2.2 kHz. After printer. digital -to -analog conversion, a signal suitable for telephone -line How will that be done? Sony's engineers have done some transmission is obtained. thinking about the matter, and have come up with a system they One problem with magnetic -reproduction devices (like the believe will work. It's much like an amateur radio slow -scan Mavica playback unit) is jitter. While it is not apparent on a TV television setup, except that it works via telephone. screen, it is something better done without. To eliminate the

TELEPHONE A/D -1SEMICONDUCTOR D/A VIDEO - TO TV OR FROM TELEPHONE --- DEMODULATOR --rI PROCESSING -- INTERFACE CONVERTER ^'I MEMORY CONVERTER COLOR VIDEO- CIRCUIT PRINTER fi ADDRESS - CONTROL CIRCUIT TIMING - OSC CONTROL R BLOCK

FIG. 7-THE TELEPHONE -LINE RECEIVER converts the slow incoming analog information to digital form so it can be stored, then converts it back to a high-speed analog signal for display. continued on page 78 j m LIS tT d IS 40 1^; m Itw fiapx

In this article we'll look inside Kodak's new needed. Without the flash, pictures can be taken every 0.4 disc camera-a good example of how elec- seconds. With the flash, that increases to about one second, due to the flash -capacitor charging time. There is no exposure in- tronics have made the picture -taking pro- dicator needed and the film advance is automatic. Needless to cess easier than ever. say, all four models use disc film. Now that we've seen the similarities, lets look at the differences between the four disc camera models. First, we'll look at MARC STERN "extra" features. Both the 6000 and 8000 have a close-up lens (18 inches to 5 feet) that is simply slid (with a lever) in front of THE EARLY ADVERTISING CLAIM OF EASTMAN KODAK, "You the normal lens. A close-up indicator is seen in the viewfinder push the button; we do the rest!" is now more true than ever. when that lens is chosen. All of the models have a metal carrying When Kodak was designing their new disc camera, their inten- strap, but the 6000 and 8000 also have a protective handle/cover tion was to develop a decision -free photo system. And thanks to that covers the entire front of the camera. (It can also be used to the miniaturization allowed by the continuing advances in mic- stand the camera up.) Only the 3000 is not powered by two roelectronics, that camera maker has been able to produce small 3 -volt lithium batteries. Instead it uses a replaceable 9 -volt but sophisticated snapshot cameras that allow the photographer alkaline battery. In the other models, the lithium batteries are to simply aim and shoot . While other camera manufacturers considered to be an integral part of the camera and, as such, are have followed Kodak and are producing their own disc cameras, covered by the five-year warranty. we will discuss only those from Kodak. The 8000 has three features that none of the other models What are the features of the disc cameras? There are four have: a motor drive that permits rapid firing by holding down the models from which to choose: the 3000, 4000, 6000, and 8000. shutter button; a 10 -second self timer (with flashing LED and Essentially the four models are the same, but they differ in some audible beeper), and, located in the cover, a digital alarm clock features and, of course, price. (The models' price range is from with its own power supply. $56.95 to $142.95.) Let's first look at the features that all models have in common,; then we will took at the differences. Nothing could be easier Each model has a 4 -element, f/2.8, 12.5 -mm, fixed -focus Before we look at the electronics inside of the Kodak disc (four feet to infinity) lens. Each also has two automatic exposure cameras, let's take a look at how you would operate one of them. settings. The flash is built in and operates automatically when The first step, of course, is to load the film. The film -loading FILM IDENTIFICATION NUMBER

v CHARGING CIRCUIT TRANSFORMER J

FIG. 1-THE DISC CAMERA might be the easiest -loading camera yet.

process consists of lifting a lever which locks and unlocks the FIG. 2-COMPONENT SIDE of the disc camera's circuit board. camera door, then dropping the disc film in place, as shown in Fig. 1, and then closing and locking the film door. That is a pretty simple method of doing things, and the film can be inserted in only one direction. However, that simple TABLE 1 action launches an intricate interplay between camera and film Swich Function as a complex locking and disc -engagement sequence begins. S1 Power switch. Actuated by camera cover or lens cover. When the disc is inserted into the camera, teeth on the core of the S2 -a Soft -touch shutter switch. film disc engage lugs in the camera. Those lugs drive the film Starts wake-up. and work in conjunction with notches in the film and a metering S2 -b Shutter switch. (Shutter button must be fully pawl in the camera to automatically position individual nega- pressed.) Starts picture -taking cycle. tives for exposure. S3 Synchronizes flash with opening of shutter. Locking the camera door actuates a lever in the camera which S4 Tells control IC when film advance should start and rotates the disc's dark slide. That slide protects the undeveloped stop. This switch is open when the metering pawl'is film from light. When the camera is opened, the dark slide is extended (in a film perforation). swung back into its protective, locked position. S5 Works in conjunction with S4 to tell control IC when With the camera ready for action, the photographer opens the the film is finished. lens cover, places the camera to his eye, looks through the viewfinder, and presses the shutter button.

Decision -making electronics decision -making process. All of the delay times are listed in We could say that it is at this point that the electronics Table 2; their function will become clear as we discuss them.) developments enter the picture. But that's not really true. The DELAY 8 routine is the maximum time alowed for a camera Actually, the electronic process is initialized when lens cover or cycle to occur. After that time, the camera will automatically go the cover/handle is opened, or when the shutter button is lightly into its battery -conserving "doze" mode. For example, if you touched. Those actions "wake up" the camera's electronics and push the shutter button with no film in the camera, the motor will start the charging of the flash -capacitor. run for only 2.4 seconds. As you can see from the flowchart, the The major portion of the disc camera's electronics is con- 18 -pin Kodak -designed control IC is also activated (S1 is tained in two custom IC's-the light -sensing IC and the control closed) whenever the shutter button is lightly touched. IC. Those IC's and the rest of the camera's circuit board is We should take some time here to talk about the shutter shown in Fig. 2. We'll look closer at those two IC's in a little switch. The contacts for that switch can be seen in Fig. 4. Unlike while. First, though, let's take a look at what they and the rest of the electronics do. Figure 3 is a simplified flowchart of the camera operation. Although we would like to show the complete decision -making TABLE 2 process, that flowchart is simply too big. Also, the flowchart for Model Model the model 8000, because it contains a rapid -sequence mode and Delay 4000 8000 a self timer, is quite complex. Therefore our simplified flow- time Function 6000

chart does not cover the 8000. Also, to avoid confusion, we will 1 Delay for measuring exposure 10 ms 12.8 ms say here that for the rest of the article, unless we specify 2 Maximum time to top -off flash charge 716 ms 1 sec otherwise, we will be referring to the model 4000. 3 Protects against S4 bounce 3.36 ms 3.36 ms The electronic process begins when the lens or camera cover 6* Self -timer: 1 -second interval for - 7.37 sec is opened. When that happens, switch S l in the camera is beeper/flashing LED closed, and power is applied to the circuit board. (Figure 4 7 Total time for self timer - 9.83 sec 8 for 2.4 sec 3.2 sec shows some of the camera's switches and their locations and Maximum time allowed picture-taking cycle Table 1 lists the functions of those switches.) That starts the *Delay -times 4 and 5 are not presently used by Kodak. "wake-up" routine and initializes the DELAY 8 routine. (That is one of several delay times that are used by the camera in its 28 START

CHARGER ON

WAKE UP DELAY 8

CHARGER OFF MOTOR COUNTER- CLOCKWISE

SEE NOTE

CHARGER ON FLASHI

DELAY 1 DELAY 2 YES DELAY 8 CHARGER OFF

DELAY 8 NO CHARGER OFF FLASH DOZE OFF MOTOR COUNTER- CLOCKWISE

NO NOTE AT THIS POINT, THE CONTROL IC CHECKS S5 TO SEE IS FINISHED. IF IT IS NOT, AND CHARGER OFF WHETHER THE FILM MOTORCOUNTEF- IF THE FILM IS METERED, THE IC CHARGES THE FLASH AND WAITS FOR S2 -b TO CLOSE. CLOCKWISE IF THE FILM IS FINISHED, THE MOTOR IS TURNED OFF AND THE CAMERA GOES INTO ITS OOZE MODE AFTER DELAY -8 TIMES OUT.

FIG. 3-SIMPLIFIED FLOWCHART of the disc camera picture -taking pro- CHARGER OFF cess. A diamond that reads "S2 -a?" is asking if that switch is closed. A MOTOR block that reads "Delay 8" means the delay 8 routine is initialized. A CLOCKWISE diamond that reads "Delay 8?" is asking if that delay has timed out. most cameras, the switch is electronic, not mechanical. Actually Pushing the button it's a bit unfair to say that-the switch was well engineered However, if the shutter button is fully depressed (thus closing mechanically. Whenever it is even just lightly touched, S2 -a S2 -b), the camera shifts into its "photo mode." As shown in the closes and the charging circuit tops off the capacitor charge. flowchart, the control IC first initializes various delay times and Because most people usually rest their finger on the shutter the flash charger is turned off. Next, the camera has to decide before they actually press it, S2-a is an almost fool -proof method between a high- and low -light state. During DELAY I, the control of keeping the flash circuit ready to shoot. IC checks the output of the photo -sensor IC. That IC measures After the camera is in its wake-up mode and the flash capaci- the ambient light level and acts as a comparator, determining tor is charged, the next thing the control IC does is to check whether or not the light is above 125 fL (footlamberts-a unit of S4-the switch connected to the metering pawl. That switch lets luminance). the control IC know whether or not the pawl is in one of the If the output of the photo -sensor IC indicates that the light film's perforations. If the film is metered (if the pawl is in a level is above the 125-fL level, the control IC initiates the perforation), then S2 -b, the shutter button is checked. 1f the high -light mode. The charger is turned off; and the motor is switch is not closed, the control IC will charge the flash capaci- turned clockwise. The clockwise motion of the exposure cam, tor, if necessary, and will then put the camera into the shutdown which is driven by the motor, sets the shutter speed to 1/200 or doze mode. second; sets the aperture to f/6; cocks the shutter, and then snaps the shutter. The last thing that the exposure cam does in its cycle is to pull the metering pawl out of the perforation in the film. That is important-as you can see in the flowchart, when the pawl is out of the film perforation, the control IC knows that the picture has been taken. It then orders the motor to turn counterclockwise to advance the film. If the light level is below 125 footlamberts, then the the light -sensing IC sends that information to the control IC. That initiates another series of actions-the low -light mode. First the charge on the flash capacitor is checked until either the charge is vD sufficient or until DELAY 2 has timed out. Then the charger is turned and the motor is turned counterclockwise. This time, SHUTTER -SWITCH I off CONTACTS however, turning the motor counterclockwise does not advance (52-a. S2-0) the film because the metering pawl is still in one of the film perforations. Instead the counterclockwise motion of the exposure cam sets the shutter speed to about 1/100 of a second and opens the aperture off/2.8. Next the control IC looks at S3. That switch is closed whenever the shutter opens and is used to trigger FIG. 4-THE DISC CAMERA consists not only of electronics. Various mechanical sensors are essential for its operatio,1. Don't open your disc the flash. camera to look at them, though. First, you will probably damage the camera and void your warranty. Second, you might damage yourself-the After the picture flash capacitor is a very real shock hazard. After commanding the motor to turn, the control IC checks S4. (Remember, the last thing that the exposure cam does in its cycle is to pull the metering pawl out of the film perforation. That closes S4.) When that switch closes, it indicates that the picture has been taken. The control IC then turns off the charger and drives the motor counterclockwise to advance the film. :ILM Two custom IC's DENTI FI CATION DUMBER IN As we mentioned previously, the major portion of the camera 3AR-CODE F)RM electronics is contained in two Kodak -designed custom IC's. Let's look first at the control IC. The control IC is an LSI integrated -injection logic (l2L) integrated circuit. That type of logic was used because it allows combining both power and logic control on the same device. (About one half of the chip's area contains power transistors.) When the camera's motor is running, the control IC's output drivers can sink up to two amps and dissipate over 1.5 watts. On the other hand, when the camera is in its doze mode, the IC uses only 90 microwatts. If a more familiar approach, such as CMOS technology, was used, both power control could not have been included on the single IC. Thus, using I`L helps keep costs, size, and power consumption to a minimum. The control IC contains an on -chip voltage regulator. That's necessary because during the picture -taking cycle, the battery FILM voltage varies (from 2 to 8 volts) as the motor is used. Also on IDENTIFICATION the chip is a 10 kHz clock. As you can see from our discussion on NUMBER the delay times, that clock, plays a very important role in the decision -making process of the disc cameras. In the 8000, it also FIG. 5-A DEVELOPED FIL A C Sc. Note that each f -ame is numbe ed. That controls the self -timer. That includes flashing an LED and makes ordering reprints very easy. pulsing a beeper-and doubling the flashing/pulsing frequency about 2.5 seconds before the exposure. The light -sensing IC measures the ambient light level and sends a one -bit output to the control IC to tell it whether or not the light level is over 125 fL. The photometer and the threshold - detection circuitry are on the same chip. That helps to reduce the chance of electrical noise causing an error. The clock in the control IC and the detect circuitry in the light -sensing IC are both wafer calibrated. That means that the chip is modified while it is still in wafer form. That helps to reduce costs because it eliminates the need for further calibration in the camera. It also helps to achieve better quality control. Once you've finished taking the pictures, the electronics processes don't stop-they continue during the photofinishing process. On each film label and on the disc itself (see Fig. 5) is a bar code pattern called the film identification number or FID. And the film core is magnetic-styrene impregnated with iron oxide. That means that instructions can be recorded there to be read by special photofinishing equipment. Figure 6 shows a console that prepares disc negatives for reorders. Reprint FIG. 6-THIS CONSOLE lets th e operator encode it formation in C e disc's magnetic core. That information can be read automatically by special quantities, frame number, and even color/density corrections printers. can be recorded on the film's magnetic core. R -E

30 Auto exposure and Auto focus Systems

Autofocus and auto - exposure systems have re- volutionized modern photography. In this article we'll look at those systems and see how they've made picture taking simpler than ever imagined. MARC STERN

HAVE YOU EVER STOPPED TO THINK ABOUT HOW PHOTOGRAPHY logic is designed to maintain the fastest possible shutter speeds has changed over the past few years? For one thing, taking a as light dims. If the shutter speed will be '/so second or slower, picture, even under adverse conditions, has become simpler the camera will give an audible signal (assuming that feature is than ever. Powerful electronic circuits provide so much control switched on) to warn the photographer that blur from subject/ over the various camera functions that essentially all a photo- camera movement is possible. grapher has to do is focus and shoot. And, with some cameras he In the aperture -priority auto mode, the photographer sets the doesn't even have to focus; that chore is handled for him by an aperture manually and the camera automatically sets the best autofocus system. shutter speed. All this has been made possible by the microelectronics In the metered/manual mode, the photographer can take "revolution" and the resulting development of LSI (Large - advantage of the X -700's through -the -lens center -weighted Scale -Integration) techniques. Using LSI technology, camera averaging meter system, while maintaining full manual control manufacturers have been able to combine many control func- over the exposure setting. When using that mode, both the tions on a single IC. The result is a generation of "cameras that shutter -speed and the aperture can be varied to achieve any think." desired effect. Highly sophisticated electronics can be found in everything All important information is displayed in the viewfinder. from "simple" snapshot cameras to professional photographic Simply placing your finger on the touch -sensitive shutter release equipment. One example of the state of the art in 35mm photog- begins metering and activates all of the viewfinder displays; the raphy is the Minolta (101 Williams Drive, Ramsey, NJ 07446) displays remain active for 15 seconds, or for however long your X-700 system. It offers just about every camera feature currently finger remains on the button. available and consists of the camera itself, an autoflash, a motor In the program mode, a green "P" lights in the viewfinder drive, a multifunction back, and a wireless remote control. above the shutter -speed scale. Red LED's along the shutter- We'll discuss those accessories shortly, but first let's look at speed scale indicate which shutter speed is being set by the what makes this camera so special. camera. Because the shutter -speed settings are stepless, if two The X-700, shown in Fig 1, features a new faster -speed - LED's light, the shutter speed is between the two indicated priority program -mode, plus an aperture -priority auto mode and values. The minimum aperture of the lens you are using appears a metered/full-manual mode. Those modes allow a photo- in the aperture window at the bottom of the viewfinder (that is grapher the choice between automatic and manual picture tak- not necessarily the aperture at which the picture is taken). The ing. lens should be set at its minimum aperture in the program mode. In the program mode, the camera automatically selects both If it is not, or if a non -Minolta MD -type lens is used, the green aperture and shutter speed for the best exposure. The system "P" in the viewfinder will flash. That indicates that the cam- FIG. 1-THE MINOLTA X700 represents the ultimate in autoexposure technology and flexibility. If features a program mode in which both the aperture and the shutter speed are determined by the camera, an aperture - priority automatic mode, and a fully metered manual mode.

FIG. 2-TWO PHOTOCELLS are used for metering. One, on the camera's light. The other. located next to the mirror era's range is reduced, and brighter subjects can not be accomo- pentaprism, measures ambient box, is used for direct autoflash metering. dated. New Minolta MD lenses can be locked at their minimum aperture. Similarly, a red "A" lights above the shutter -speed scale to stopdown, and mirror lift. A 42 -pin BiMOS IC handles meter- indicate when the camera is set in the aperture -priority automatic ing, calculations, and controls. Metering is done through two mode. Once again, LED's light along the scale to show which silicon photocells. One of them, on the camera's pentaprism, shutter speed is being set by the camera. The lens aperture that measures ambient light, while the other, located next to the you select is clearly visible in the window at the bottom of the mirror box, is for direct autoflash metering (see Fig. 2). The viewfinder. output from the photocells is fed to the BiMOS IC, which In the metered manual mode, a red "M" lights in the viewfin- amplifies and processes the signal. Of the remaining IC's, a der, the aperture setting is shown at the bottom of the viewfin- 42 -pin bipolar device handles mode selection and program - der, and an LED lights next to the shutter speed that will provide mode operation; a 44 -pin I2L (Integrated Injection Logic) dot - proper exposure according to the light metered through the lens. display driver handles the viewfinder displays, and a 12 -pin Note that this is not the actual shutter speed; both the aperture bipolar device handles the electromagnetic shutter release and and the shutter speed must be set manually, and either setting power control. can be adjusted without affecting the other, affording maximum To better appreciate all of the complex functions that this flexibility. control system must handle, let's take a closer look at all the The camera also has two features that allow for more creative steps involved in producing a successful photograph. To keep control and better results when using automatic exposure -setting things as simple as possible, we'll only look at what happens in under unusual lighting conditions. The ± 2EV exposure adjust- the program mode. ment allows you to vary the automatic exposure setting up to As we said earlier, in the program mode the camera sets both more or less two f-stops from normal in the program and automa- the aperture and shutter speed, with preference given to using tic modes. When that feature is used, a ± LED blinks in the the fastest practical shutter speed. Touching the camera's touch - viewfinder. The auto -exposure lock feature is useful when the sensitive operating switch inputs preset camera -setting informa- subject makes up but a small part of the total picture. It is tion and scene brightness into the program -mode circuitry. especially useful, for example, if your subject is in the shadows When the operating button is fully depressed, the camera re- but his background is strongly lighted. Normally, the camera trieves a programmed aperture value from the camera's memory would be "fooled" and set its exposure by the bright light-but based on that information. The aperture is then set, and the light not with the auto -exposure lock. When that feature is used, the passing through the aperture is re -metered as a final check before subject is metered at close range and the AE -lock switch is shutter operation; sensitive metering and fast reaction time al- pressed down. While that switch is held down, all you have to do lows the settings to change instantly with changing light con- is move back, recompose the picture, and then release the ditions. All of that happens in milliseconds. shutter. The camera's electronics also control the flash, when that unit In -the -viewfinder indicators of the status of the autoflash are is required. When the flash capacitor is fully charged, a signal is also displayed when that unit is attached. Among the informa- fed from the flash unit to the camera. When the shutter is tion available is whether the flash is fully charged, insufficiently released, the shutter speed is automatically reset to 1/60 second charged, or off. In the last two cases, the settings for the ambient and the appropriate aperture is determined. After the mirror lifts, light conditions are displayed and, if the shutter is released, the flash emits light simultaneously with full shutter opening so those are the settings at which the camera will operate. Once the that light reflected from the subject strikes the film surface. The shutter has been released, another in -viewfinder indication silicon photocell next the the mirror box collects a sample of that shows if the proper exposure has been made. reflected light and shuts off the flash at the precise moment for best exposure. A feedback system indicates both in the camera's What's inside viewfinder and on the back of the flash whether the exposure The Minolta X-700 uses five integrated circuits. At the heart was correct. of the camera is a 32.768 -kHz oscillator that provides 1/30,000 - second accuracy. The output from that oscillator feeds a 42 -pin Accessories CMOS IC that controls the timing of most of the camera's The Minolta X-700 system includes all of the accessories you functions. Those functions include shutter release, aperture would expect to find in such a camera system, and more (see PHOTOCELL

SONAR LOGIC AND RECEIVE CIRCUITRY

FIG. 3-ACCESSORIES for the X-700. Of particular interest are the dedi-

cated flash, the multifunction back, and the remote -control set. SONAR TRANSDUCER

FLEXIBLE PC Fig. 3). Aside from the wide variety of lenses, motor drives, ATHlAI etc., those accessories include an automatic flash, a multifunction back, and a wireless remote control. We'll next look at those three units and see what makes them special. FIG. 4-INSIDE THE POLAROID 660. This autofocus camera uses an active sonar system. We've already looked at the Electroflash 280PX autoflash unit a bit. It is a clip -on programmed/automatic/manual flash unit with special contacts for both camera control and through - receiver is designed to attach to the camera's accessory shoe, or the -lens, off-the -film flash metering. The flash duration varies to a special bracket included in the set. between 1/50,000 and I/1,000 -second, depending on light con- The wireless control uses near -infrared pulses for com- ditions. No adjustments or settings are made on the flash unit munications. That technique avoids problems such as in- itself because that unit receives all needed information, includ- terference and spurious signals so common to radio control. (But ing the speed of the film being used, from the camera. the range of the unit can be affected by adverse weather con- Perhaps the most interesting accessory for the camera is a ditions such as direct sunlight or fog and Minolta recommends unique multifunction back. Containing its own dedicated pro- that operation under actual conditions be checked before any cessing unit, that device mounts in place of the X -700's regular photographs are taken.) Under ideal conditions, communication back. What makes it so interesting is that it offers camera - over distances as great as 200 feet are possible. That com- control modes for time-lapse photographs, timed long - munication need not be line-of-sight-the infrared pulses can be exposures, and multi -frame sequences. In addition, it features bounced around corners or off surfaces. Finally, the unit boasts six data -imprinting modes to be used for identifying and three independent channels so that up to three cameras, or three classifying photographs. groups of any number of cameras, can be controlled in- A highly accurate quartz clock and auto calendar that runs dependently. from 1981 through 2099 imprint the time in hours, minutes, and seconds, or the date. Once set, the calendar will advance, taking Autofocus into account leap years and differing month lengths. The calen- Autoexposure is just one way that electronics has changed the dar will also print the date in any order of year/month/day way we take pictures. There are, of course, others. Consider preferred. Other modes imprint any number from 1 through autofocus, for instance. A few years ago, those circuits were 999,999 for any coding scheme you like, or will sequencially bulky, expensive affairs. With the introduction of integrated count the frames. circuits and large-scale integration, the autofocus circuitry can All of that would make that accessory nice in its own right, but now be placed on IC's little larger than a postage stamp; what's there is much more. For one thing, long, unmanned exposure more important for consumers and manufacturers alike is that times of up to several hours are possible. Another feature is the IC's are not costly to manufacture. Autofocus has thus unmanned interval-photography. That allows the camera to take become common on many relatively inexpensive cameras. photographs automatically at pre -determined intervals of be- Autofocus systems can be grouped into two classifications: tween 1 second and 99 hours, 59 minutes, 59 seconds. Once the active and passive. In an active system, the camera bounces a interval between photographs is determined, the camera is sim- signal of some type (usually an ultrasonic tone or infrared pulse) ply set up and left alone. Interval flash -photography is even off of an object, and uses the reflection to calculate the distance possible; the multifunction back turns on the flash unit one and set the focus. In a passive system no signal is emitted; the minute before the interval expires. That feature requires the use camera judges the distance from the subject using optical and of an autowinder or motor drive. electronic means. All the special back's functions are accessed and programmed Let's first examine active systems. The principles behind a using six keys and a slide switch that are concealed under a cover sonar system, such as that used in Polaroid's (549 Technology on the rear of the camera when not needed. The data imprinting Square, Cambridge, MA 02139) 660, should be familiar to is handled by a series of LED's within the back and the interfac- most. The camera emits an ultrasonic pulse and measures the ing between the back and the electronics of the camera itself is time it takes for the echo to return. done through three spring -loaded electrical -contact pins. Let's take a close look at the 660 (see Fig. 4). When the The last accessory we'll look at is one that is usually associ- shutter button on the camera is first pressed, a 50 -kHz sound ated with cameras costing far more-a wireless -controller set. burst is generated by a transducer mounted on the front of the The set consists of a small transmitter that resembles a spot camera. When the sonar echo returns to the camera, it is pro- lightmeter and a receiver that resembles a small flash unit. The cessed by the sonar logic and receive circuitry, shown in Fig. 5, 33 X- SUBJECT

SUBJECT DISTANCE = Y:B TANG

FIG. 5-THIS PC BOARD holds the 600's sonar logic and receive circuitry. which computes the elapsed time and stores it. From that in- 2 -ELEMENT DETECTOR ON formation, the camera selects the proper supplementary lens PIVOTING MOUNT TO DETERMINE O (there are four mounted on an internal disc) and rotates it into IR system. This technique, used by Chinon, position, where it is latched and held. With that lens in position, FIG. 6-AN ACTIVE autofocus is based on triangulation. the camera will be properly focused. At the moment that the disc is latched, a solenoid releases the shutter blade and a silicon photodiode measures the ambient Turning to passive autofocus systems, most use either light level. Information from that photodiode is instantly evalu- triangulation or analyze the image produced by the lens to ated by the camera's electronics. If the light is greater than 10 determine focus. candles -per -square foot, the fill -flash mode is selected; at lower Passive triangulation systems work much like manual range- light levels, full flash is selected. The flash will fire for all finder cameras in that the camera is focused by moving the lens exposures unless manually overridden. As the shutter blades until the two images in the viewfinder correspond. Typical of continue to open, the flash fires at the precise moment and at the such systems are Honeywell's (Honeywell Plaza, Minneapolis, correct aperture as selected by the camera's exposure - MN 55408) Visitronic and Canon's (One Canon Plaza, Lake determining logic circuitry. Those factors are determined by the Success, NY 11042) SST or Solid State Triangulation. distance between subject and camera. The measured ambient Those systems use arrays of photodiodes to compare the light level is used to determine the duration of the flash, and the images. Where the systems differ is in how they compare those distance and the light are used to determine how long the shutter images. The Honeywell system uses one moving image and one remains open. fixed one, much like manual rangefinders. The images are The camera's electronics complement consists of the photo- examined by the arrays until they coincide. In the SST system, diode, an analog circuit that controls the transmission and recep- the images are fixed. Two arrays of photodiodes examine the tion of sonar signals, a voltage -to -frequency converter, a power images, and the signals from those devices are analyzed to IC, and the exposure -mechanism logic network. determine the difference, and hence the distance. The camera, including the flash system, is powered by flat There are two autofocus systems that work by analyzing the batteries developed especially for the 600 series of cameras. image: contrast detectors and focal -plane detectors. Contrast Those batteries are part of each film pack. detecting systems, used in cameras such as the Canon AL -1 and An active infrared system, such as that used in Kodak's the Pentax (35 Inverness Dr. E., Englewood, CO 80112) ME -F, (Rochester, NY 14650) Kodamatic 980L, measures the bright- are based on the premise that when the contrast is at a maximum ness of a reflected pulse. That system can run into difficulty, (that is, when the variation in brightness from point-to-point is at however, if the object being photographed is more reflective a maximum) the image is in focus. Photodetector arrays that are than average. Fortunately, most objects reflect infrared about centered around the focal plane, but located at slightly varying the same way, and though the system is not totally foolproof, the distances from the lens, and a microprocessor are used to meas- slight differences that do occur are unimportant considering the ure that variation in contrast. camera's small -aperture lens. Focal -plane detectors are a bit more complicated, at least in A variation on the infrared technique uses triangulation to concept. They work on the principle that the light from different determine distance. In that system, the baseline runs between points on an out -of-focus subject strikes each point in the film. If the camera's infrared emitter and detector and the peak of the those points have contrast (that is if their brightness varies) the triangle is at the photographic subject. The distance from the aperture will appear to be unevenly illuminated. Conversely, the camera to the subject is then found by measuring the base angle image will be in focus only if the aperture is evenly illuminated. of the triangle. That measurement can be done either electroni- Thus, to check for focus all that need be done is to use a matched cally or mechanically. For instance, a camera might use a set of pair of photodetectors to look through opposite halves of the photodiodes in a rotating mount. That mount is tied to a motor aperture. When both detectors see the same thing, the camera is that rotates the diodes until the signals at both are equal. When focused. that happens, it means that both are pointed at the area that From what we've seen so far one thing is clear-that thanks to reflects the most infrared, which is the object to be photo- new advances in microelectronics the nature of photography has graphed. The same motor is also tied to the lens in such a way changed dramatically. Although it may appear that you're only that it is focused on the area that is indicated by the triangulation. pushing a button, what's going on inside the camera is making it The system described is used by Chinon (43 Fadem Rd., Spring- possible to take pictures under all kinds of conditions with field, NJ 07081) and is shown in Fig. 6. amazing results. WITH CIE, THE WORLD OF ELECTRONICS CAN BE YOUR WORLD, TOO.

Look at the world as it was 20 START WHERE YOU years ago and as it is today. WANT, GO AS FAR AS Now, try to name another YOU WANT. field that's grown faster in CIE's broad range of entry, those 20 years than electron- intermediate, and advanced ics. Everywhere you look, level courses in a variety of you'll find electronics in career areas gives you many action. In industry, aerospace, options. Start with the Career business, medicine, science, Course that best suits your government, communications talents and interests and go as -you name it. And as high far as you want-all the way, technology grows, electronics will if you wish, to your Associate in grow. Which means few other fields, Applied Science Degree in Elec- if any, offer more career opportunities, tronics Engineering Technology. But more job security, more room for ad- wherever you start, the time to start is vancement-if you have the right skills. now. Simply use the coupon below to send for your FREE CIE catalog and SPECIALISTS NEED INDEPENDENT STUDY BACKED BY PERSONAL complete package of career information. SPECIALIZED TRAINING. Or phone us at 1.800.321.2155 It stands to ATTENTION. reason that you learn (in Ohio, 1-800-362-2105). Don't wait, anything best We believe in independent study from a specialist, and CIE ask for your free catalog now. After all, is the largest because it puts you in a classroom of independent home study there's a whole world of electronics out one. So you can study where and when school specializing exclusively in there waiting for you. electronics, with a record that speaks for you want. At your pace, not somebody itself. According to a recent survey, 92% else's. And with over 50 years of of CIE graduates are employed in experience, we've developed proven electronics or a closely related field. programs to give you the support such When you're investing your time and study demands. Programs that give you money, you deserve results like that. the theory you need backed with practical experience using some of the most Cleveland Institute of sophisticated electronics tools available Electronics, Inc. anywhere, including our Microprocessor 1776 East 17th Street Training Laboratory with 4K of random Cleveland, Ohio 44114 access memory. Of course, if you ever 216-781-9400 have a question or problem, our instructors are only a phone call away. A half century teaching electronics. B M ------RA -o5 Cleveland Institute of Electronics, Inc. 1776 East 17th Street, Cleveland, Ohio 44114

YES...I want to learn from the specialists in electronics-CIE. Please send me my FREE CIE school catalog, including details about CIE's Associate Degree program, plus my FREE package of home study information. Print Name Address

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Age Area Code/Phone No. / Check box for G.I. Bill bulletin on educational benefits: Veteran Active Duty MAIL TODAY! IF YOU'VE BEEN AN AMATEUR PHOTO- grapher for more than just a few years, you probably remember when the state of the art in photo accessories was a strobe unit that was about the size of a hammer and weighed just about as much. They were the ones that also required an outboard 9- or 12 -volt battery pack to drive the flash tube. And after a couple of hours of use they felt as if they weighed several hundred pounds. Obviously, the scene has changed radically today- many cameras, even inexpensive ones, have built-in strobe units that are powered by a couple of penlight batteries. But the serious amateur photographer has available to him "smart" strobes that can communicate with "intelligent" cameras to produce high -quality photos. These smart strobes boast the same light output as their ancient relatives, but they do more, and are much smaller. In fact, some are so small they can literally fit in your shirt pocket with room to spare. And strobes aren't the only photo accessories that have seen some radical changes during the last 20 years. Remember the old light meters? They were handheld affairs that offered good accuracy, but using one required spinning dials and matching needles. Today's advanced light meters, while still about the same size as their counterparts from the 1960's, have lost all of their dials and needles. Now built-in microcomputers and LCD readouts make finding the right exposure setting easier than ever. Photo Accessories Camera accessories have not been left out of the "electronic revolution." Microprocessors, memories, and LCD's are among the features that you'll see.

MARC STERN

Strobe units the shutter speed, select a suitable aperture, activate viewfinder Before we look at individual strobe models, let's take a look at information (such as a flash -charge indicator), and control flash what a strobe does, how it works, and some features it might duration-then what you need is a dedicated strobe unit. contain. What makes one strobe setting different from another is not Some strobe units cannot be adjusted-they flash for a given how bright the unit fires. Rather, it is the length of time that it length of time. They usually contain a "computer" dial. To use fires. With the non -automatic strobe that time is constant, and to them, you first dial in the film's ASA number. Then you can dial obtain the correct exposure you have control only over the f-stop in the distance from the subject and read off the f-stop you need setting and the distance from the subject. to use a particular aperture you can dial the f-stop up on the Automatic strobes, on the other hand, use a photo cell to calculator dial, and it will tell you the distance that you should be "look" at the amount of light that is reflected by the subject. from the subject. When the strobe is used, the camera is set to its When it determines that it has received enough light for the x position; that sets the shutter speed (usually to about a sixtieth proper exposure, it then shuts off. An example of a dedicated of a second) and causes the camera to close a switch that sets off electronic flash is the Speedlight 166A, from Cannon (One the flash when the shutter opens. Canon Plaza, Lake Success, NY 11042) shown in Fig. 1. It mounts in the accessory shoe of Canon's AL -1. When the flash is Dedicated strobes fully charged, it automatically sets the camera's shutter speed to There is another type of flash unit called the dedicated strobe. '/60 second, and a light on the flash tells you that it's ready. The When the word "dedicated" is applied to strobe units, it means flash gives you a choice of two apertures; it displays them in a that that unit is tied to being used with one particular camera-or window on the back of the flash. The settings depend on the at least one made by a particular manufacturer. If you want a speed of the film that you're using. The distance ranges that are smart unit-a strobe that communicates with the camera to set available with the selected f-stop are shown on a table on the 38 FIG. 2-THE LCD DISPLAY of the 5600 modular flash system from Vivitar makes this unit very easy to use.

FIG. 1-A DEDICATED ELECTRONIC FLASH. The Speedlight 166A from numerically. If you change the f-stop, the display recalculates Canon fires from 1/50,000 to 1/1000 second. the range. The flash duration range is from 1/30,000 to 1/1000 second. back of the flash unit. When you take the picture, the strobe fires The flash operates a little differently in its manual mode-the for anywhere from 1/50,000 to 1/1000 second-automatically most significant difference being that the flash duration is al- controlled. ways 1/1000 second (it does not adjust automatically). When If you want a smart-therefore, dedicated-strobe for your switched into the manual mode, the unit signals with three camera, you don't have to be limited to buying one from your double -beeps. When you program in the f-stop, the display camera's manufacturer. Thanks to the flexibility afforded by shows the distance for the correct exposure. In the manual mode microelectronics, it is now possible for one manufacturer to you have a choice of 12 differentf-stops (as compared to eight in build a strobe unit that can be dedicated to a number of different the auto mode). As you change the f-stop, the readout changes cameras. An example of that is Vivitar's 3000 series of dedi- the display to show the optimum distance to the subject. (In the cated flash systems. It is designed to work with cameras from the manual mode the distance to the subject is more critical than in Canon, Minolta, Olympus, Nikon, Pentax, Yashica, and Con - the automatic mode because of the fixed light -output.) tax lines, as well as just about any of the other popular single- At the heart of the 5600 is a custom microprocessor that drives lens reflex (SLR) cameras on the market-provided that you buy the LCD display and accepts inputs from the strobe's photosen- the correct Vivitar dedicated module. sor unit. This unit not only accepts user inputs, but also compar- Like many other strobes now on the market, the Vivitar (1630 es those inputs against preprogrammed, proprietary logic and Stewart St. , PO Box 2100, Santa Monica, CA 90406) 3500 uses derives the display figures. This unit also controls the flash energy -saving circuitry to keep the flash recycling -time down. output in the auto mode and contains all the system driver - On units without that circuitry, when the flash has fired long circuits. enough for correct exposure, the rest of the charge on the flash In the AUTO mode, you can check whether or not the exposure capacitor is "dumped." With the energy -saving circuitry, selected will work by firing the flash manually (without snapp- however, the unused charge can be recycled, thus saving the ing a picture). If an acceptable picture will result, the AUTO batteries and reducing the flash charging -time. That means that symbol flashes. (An audible signal can also be enabled.) The the flash can sometimes be used with an autowind camera, AUTO symbol will also flash after you take a picture if the amount depending on the distance to the subject. (The farther the dis- of light was sufficient for proper exposure. tance, the longer the flash has to fire, and thus the longer the The LCD also indicates the angle of coverage for the flash recycling time.) head being used. (There is a variety of heads available for the Vivitar's 5600, though, is a better example of an electronical- 5600, including a zoom head.) ly advanced strobe unit. It is shown in Fig. 2. Like the 3000 Special voltage-sampling/timing circuitry also enables the series, dedicated processor modules are available that let you microprocessor to flag weak batteries. If the batteries fail to interface the 5600 to a wide range of popular cameras. Another recycle the unit within 35 seconds, the battery -replacement module is available with a PC cord that allows you to adapt the symbol is activated. (The normal recycle time is less than 12 flash unit to non -dedicated cameras. The feature of this strobe seconds if alkaline batteries are used, and less than 7 seconds if that sets it apart from others is its LCD readout. That readout the optional nickel -cadmium battery pack is used. A "star - eliminates confusing calculator dials and mathematical burst" is seen in the display when the flash is fully charged.) The computations-all the information you need to know is dis- warning symbol indicates that the batteries can still be used, but played in easy -to -read form. Let's take a look at how you would that they are in a weakened condition and should be replaced use that strobe, first in its automatic mode. As we discuss the soon. LCD readout, refer to Fig. 3 Like the other strobes in this line, it is possible to use this one When you first put the flash unit in its automatic mode, an with any of the popular single-lens reflex cameras by employing AUTO indicator is displayed and the the unit beeps three times. special processor modules. These modules contain the neces- (That, and all of the unit's audible indicators, can be switched sary electronics for interfacing the strobe head with the electron- off if silence is necessary.) Then you tell the 5600 the speed of ics inside the new generation of "intelligent" cameras. your film (using either ASA or DIN standards). Next you tell the Vivitar isn't alone in offering this type of flash, either. The unit the f-stop (eight choices from f11.4 to f116) you want to use. major camera manufacturers, among them Pentax, Minolta, and The flash range then appears on the display (in either meters or Canon, also offer dedicated units that interface with, and take feet) on a bar graph. Also, the maximum distance is displayed advantage of, the electronic circuitry in their equipment. ASA/ISO FLASH -RANGE MAXIMUM t--STOP INDICATOR IN AUTO -MODE FLASH RANGE

AUTO -MODE ANGLE OF COVERAGE LOW -BATTERY INDICATOR FOR HEAD IN USE INDICATOR

FIG. 3-A CLOSE UP VIEW of the 5600's LCD display shows just how much exposure information it can provide.

Light meters Most photographers rely only on their camera's built-in light meter for their exposure measurements. And with the quality of those built-in meters, you might be wondering why anyone would want to use anything else. Serious photographers, however, often do want to use an accessory meter. That's because there are many instances when the readings from the FIG. 4-ALTHOUGH COMPLEX INTERNALLY, the Auto Meter III from built-in meter are too general. And that's why the hand-held Minolta is a snap to use. light meter is still around. It can help eliminate a lot of the extra exposures and guesswork that often go along with getting just the right shot. But today's light meters are not what they were all three readings are always displayed on the dot array. even a few short years ago. That the microprocessor provides versatility is apparent from Before we start discussing how they have changed, let's the fact the photographer can change the film speed set, or the clarify what we mean by saying that there are situations when shutter speed, even after the measurements have been taken. should use an accessory light meter. Assume that your subject is When they are changed, the microprocessor automatically ad- standing in the shadows with strong backlighting. Your built in justs for the changes and indicates the new data in the display. light meter would provide you with an exposure setting based on One of the beauties of an all -electronic meter is its reliability. the overall lighting that it sees, and the resulting picture would Since there are few moving parts, mechanical failure or wear is be underexposed-the portion you were interested in would be nearly nonexistent. not much more than a silhouette. However, with a hand-held light meter, you could determine the proper exposure setting by Spotmeters measuring the amount of light reflected by or falling on just the A spotmeter, which is a special type of reflected -light meter, subject, and not have to rely on a possibly erroneous overall is a meter for the more advanced photographer. When such a reading. meter is aimed at the subject it allows him to measure the amount This discussion of light meters will not try to be a roundup of of light from a very small area, so that he can determine the manufacturers' products; we just want to give you an idea of proper exposure setting with great precision. Minolta's Spot - what features are available due to advances in electronics. meter M, shown in Fig. 5, has a one -degree viewing angle. Therefore, we will use one manufacturer's (Minolta's) line as an That meter uses the same type of microprocessor control and example. LCD readout as the one we previously discussed, but, being a The first meter we will look at is Minolta's (101 Williams spotmeter, it allows the photographer to measure the lighting on Drive, Ramsey, NJ 07446) Auto Meter III, shown in Fig. 4. We the exact spot he wants to measure-a highlight or shadow, for find it is built around a custom-built microprocessor, the example. "brain" of the unit. Its LCD readout makes it easy to use-No Three buttons, labeled s, H, and A (shadow, highlight, and longer does a photographer have to twirl dials and match num- average), are included. When the "shadow" button is pressed bers to find correct exposure settings. the microcomputer recomputes the exposure settings so that the A memory in the Auto Meter III allows you to store one or two measured spot will be exposed as a shadow. The "highlight" measurements, which can be recalled and compared to the third button is pressed for the exposure settings so that the measured one being taken. To make the comparison easier, the f-stops of spot will be exposed as a highlight, while the "average" key all three measurements are displayed on what Minolta calls a will give the average of the other two readings. That feature is "dot -array display." They can be recalled one at a time as especially useful when taking portrait shots-it allows you to be desired. more creative because it lets you get precisely the effect that you Let's look at how you would use the meter. The first thing that want without a lot of guesswork. you have to do is to set the film speed and the shutter speed Another type of electronic spotmeter is represented by Minol- desired. Then, simply pressing the measurement button causes ta's Auto -Spot II and Auto -Spot II Digital. Like the Spotmeter the meter to compute the f-stop or EV number (you choose M, they are hand-held spot meters. The interesting feature of the which one you want) that is required for proper exposure. The Auto -Spot /1 -line is a "total -information" viewfinder that in- number is displayed both digitally and by a dot on the dot -array dicates all necessary information at a glance for proper expo- display. sure. With this meter, the scales in the finder move continuously By depressing the memory key, you can then enter that value until the trigger is released-then the readings are locked. The into the unit's memory. You can then take a second meter key difference between the two meters is that the Digital pre- reading (at a different shutter speed) and enter that one in sents a digital readout, while the Auto -Spot II presents an analog memory. one (on rotating scales). If you need a third measurement, you can take one and it will Today's light meters are very different from light meters of be instantly displayed. Then, with the RECALL key, you can the past. Their main advantage is that they can be used more recall the two previous readings. The f-stop (or EV) settings for accurately. That's not to say that the meters used years ago were

40 were not as accurate as other types of devices and they suffered from several shortcomings. They were replaced in the early 1970's by CdS (cadmium sulfide) photoconductive cells. Those allowed for more precise measurements, but they also had their drawbacks. One of the more troublesome problems was that they could develop "memories." That effect, called the light - history effect, means that the conductance of the photocell is a function of not only the light that it "sees" now, but it is also a function of the cell's previous exposure to light. The photography industry found the answer to that problem in silicon cells, which can be used as accurately as the cadmium - sulfide cells, but don't suffer from the same problems. Two other byproducts of electronic technology are flash meters, such as Minolta's Flash Meter III, and color meters. Es- sentially different types of light meters, they, too, use large- scale -integration and LCD technology to assist the photographer. For instance, the flash meter provides precise incident or reflected -light readings of electronic or bulb flash, or continuous illumination, or combinations of them. At the push of a button, a microprocessor turns the results of those readings into FIG. 5-THE SPOTMETER is a special type of reflected -light meter. Shown a display indicating the correct f-stop for a given situation so that is the Spotmeter M from Minolta. the camera can be set correctly. The color meter allows a photographer to determine what filters, if any, are needed to not accurate-in many cases they were. But because they were ensure accurate color reproduction. more difficult to use, and because they could be misused easily, A relatively new camera accessory that is becoming in- the chance of error-usually the fault of the photographer-was creasingly popular is the electronic camera -back. Some such high. backs can imprint the date or time of exposure; the film type and With older meters, the light falling on a photocell generates a exposure settings, and some can even operate the camera auto- voltage that then moves a meter needle which is read by the matically for time-lapse or long -exposure photos. We won't go photographer and, based on that reading, dials are turned so that into more detail at this time; a multifunction back was discussed the correct exposure settings can be determined. Today's meters in a previous article in this section. read the light level, take into consideration the user's inputs As you can see, photographic accessories have come a long (such as film speed and shutter speed), and then tell him the way in the last two decades, thanks to the microelectronics correct exposure settings and camera -to -subject distance in an revolution. They have given every photographer the chance to easy -to -read form. produce high -quality photos, something that everyone strives In the 1960's. selenium cells were used primarily, but they for. R -E

STANDARD TV WHITE PEAK LEVEL THE ALL -ELECTRONIC MAVICA SIGNALH HORIZONTAL Ur BLACK LEVEL continued .from page 26 SYNC HORIZONTAL SYNC

TRANSMITTED WHITE PEAK LEVEL affects of jitter on transmission, it is effectively cancelled by IMAGE SIGNAL WITH CONVERTED extracting the jitter signal from the video and using it to mod- 7 BLACK LEVEL HORIZONTAL CONVERTED 14 ulate the -MHz sampling clock. Since both signals then con- SYNC HORIZONTAL SYNC tain identical amounts of the same jitter component. it is nulli- FIG. 8-STANDARD VIDEO SIGNAL (a) compared to signal used over fied, and the sampled signal is free of that annoyance. The telephone lines (b). Note how sync is inverted and maintained at white - jitter -free digitized video is then stored in the memory of the level (as opposed to blacker -than -black) in the latter. transmitting unit. The 800 -Hz signal derived from the digital -to -analog conver- TV signal (a) and the one transmitted over the phone line by the sion process is fed to a lowpass filter to eliminate spurious Sony system (b). signals, and its level adjusted to meet the requirements of The received signal is stored in memory and undergoes phone -line transmission. digital -to -analog conversion (essentially the reverse of what was At the receiving end of the system, further steps are taken to done at the transmitting end). The image can then be viewed on a ensure the highest possible image quality. Because phone line TV screen, or printed by the Mavigraph. (You can also record signal -levels fluctuate greatly, an automatic -gain -control circuit the digital signals on a standard audio cassette, and play them using a reference signal contained in the system -control signals back when you desire.) It takes about four minutes to transmit that start each image transmission is used to adjust the received one picture by this method. signal to the proper level. The Sony engineers also realize that Although this is a somewhat simplified explanation of what the phone system has a rather poor signal-to-noise ratio, and goes on, it describes what is perhaps the most important use of have adjusted the image signal to take that into account. In their filmless electronic photography and demonstrates the ability to system, the extremes of the image signal are the levels represent- combine video with many different forms of media. ing black and white. The horizontal -sync signal, which is nor- Since the Mavica system is based on electronic video signals, mally "blacker -than -black," is inverted and extended to equal it is also compatible with other electronics equipment. It will be the peak white -level. Because the circuitry may have problems possible, then, in the long run, to use and integrate photos and differentiating between a signal that represents pure white and other pictorial matter with computer -generated reports or to one that represents horizontal sync, a vertical sync signal (also at access and use pictorial matter in other electronic ways. the 1009c level) is transmitted during the interval that contains The Mavica system has a great deal of potential in many no image. lt, and the fact that the horizontal -sync pulses occur at realms, and though we may have to wait a while before we can regular intervals, prevent the sync and image signals from use it at birthday parties, we are certain to see it widely used becoming confused. Figure 8 shows a comparison of a standard commercially. R -E

41 Electronics in The Darkroom Precise timing and repeatability of results are essential in the darkroom-especially for color processing. The use of electronics in what were previously all -mechanical devices allows a new degree of accuracy to be attained.

MARC STERN

NOT TOO LONG AGO MAKING COLOR PRINTS WAS SO DIFFICULT - National Bureau of Standards guidelines, has a range of 59° F. to especially for the amateur-that many who were proficient in 140° F. , and is accurate to ± .25 -degree F. Its probe is made of black -and -white darkroom techniques absolutely refused to get chemical- and heat -resistant plastic, and is designed to hang on involved with color. Processing times and temperatures were tanks and trays without slipping or rolling. The thermometer can critical, filtration and exposures were hard to determine, and the be powered by four 1.5 -volt "AA" cells or a rechargeable chemicals were a nightmare! It could take an entire evening to nickel -cadmium battery pack. make just one satisfactory print. The chemistry end of color processing was simplified about ten years ago, but it wasn't until Color analyzers recently that electronics made color printing really easy. We're One of the trickiest parts of color printing is color balancing- going to discuss some of the ways it has done so. it's like adjusting the hue control on an old color -TV set for correct flesh -tones, only harder. A number of variables are Temperature control involved, including the lighting conditions under which a pic- One of the most critical factors in color processing is the ture was taken and-more critical-the particular emulsion temperature of the chemicals used. Color work is much more batches used for the film and printing paper. (Each batch of temperature critical than black-and-white-some of Kodak's paper or film produced by a manufacturer varies slightly from processes require the chemicals to be within ± '/a -degree of a the ideal specifications for color properties. These have to be certain temperature (usually around 100° F.) compensated for in the printing process through the use of To measure temperatures accurately, an electronic digital filters.) thermometer like the Omega CF20 can be used. Employing Color balancing is simplified by a device called a color large-scale circuit integration and a solid-state sensor, the analyzer, which measures the color content of the light projected thermometer displays almost laboratory -precise readings on a through the negative or slide and, "knowing" the filtration 31/2 -digit LED readout. The thermometer, which is calibrated to requirements of the particular paper and film being used, de - 42 FIG. 2-THE GRALAB 20 DIGITAL DARKROOM TIMER can sound a short tone each second to permit the darkroom worker to carry out time -critical operations like dodging and burning -in without having to watch the time display.

diffuser is placed in front of the lens of the enlarger, but the FIG. 1-OMEGA's SCA 300 DIGITAL COLOR ANALYZER can accept user - device can also be used to take spot readings to determine programmable RAM modules that greatly reduce setup time. contrast, or from specific parts of a negative. Timers and color analyzers termines the filter values that must be used. It should be men- With the correct exposure information and timing information tioned that some filtration is always required; the exact amount in hand thanks to devices like the ones just described, the depends on a number of factors. Because of their cost, color photographer then can program an all -electronic darkroom timer analyzers used to be considered luxury items, but today they to turn on the enlarger for the correct length of time. Those almost have become necessities as the costs of paper, chemicals, devices can either be simple stand -alones, like the Gralab and other photographic materials have climbed through the roof. (Dimco-Gray Company, 8200 S. Suburban Rd., Centerville, Any waste of those items is needless and it is also rather OH 45459) model 500 or 520 (the latter is shown in Fig. 2), or expensive. they can have additional features. We'll see an example of that A good example of the state of the art in color analyzers is shortly. provided by Omega's (Omega Division, Berkey Marketing The Gralab 500/520 timers use a quartz crystal timebase to Companies, 25-20 Brooklyn -Queens Expressway West, Wood- eliminate interference from power lines, and to ensure accuracy side, NY 11377) microprocessor -controlled SCA 300. The SCA regardless of line -frequency variations. They can be 300, shown in Fig. 1, can accept computer -type RAM (Random pushbutton -programmed for times from 0.1 -second to 99 mi- Access Memory) programmable memory -modules; each module nutes, 59.9 seconds. is programmed by the photographer for a specific film/paper The timers provide readouts on four -digit red -LED displays. combination. With one of the modules installed, the analyzer The intensities of the displays can be set bright for high lighting - allows him to make any number of prints without missing a levels or low for good readability in total darkness. The timers beat-without his having to retest, reset, or reprogram anything. have grounded outputs for enlarger and safelight control; the When a photographer uses a particular combination again, all he enlarger and printer can be switched on or off either manually or has to do is insert the correct module. by the timer. Both units can repeat the selected time as often as The probe contains a set of three silicon cells with matched desired, ensuring fast production and identical exposures for dichroic and narrow-bandpass filters. In use, it is placed on the large print -runs. They can also generate a metronome signal at printing easel, in place of the paper, and the cyan, magenta, one -second intervals (useful if you have to time a process but yellow and exposure readings taken in sequence. Each reading is can't watch the display), and a two -second signal indicating that displayed on a 31/2 -digit variable -intensity LED readout. When the timer has reached the end of its count. The model 520 allows all the filter values and the exposure time have been determined the photographer to program two different time settings, each of and set, the probe is removed, the paper put in place, and the which can be instantly recalled. The two settings will remain in exposure made. the unit's memory until cancelled. The analyzer, which includes a feature that allows adjustment The more sophisticated microprocessor -controlled Omega of the overall color -sensitivity level without affecting stored CT-40 timer/controller (see Fig. 3) allows up to 17 sequential programs, is capable of selectively displaying the amounts of time -intervals to be stored in memory. It can be programmed to cyan, magenta, and yellow filtration needed, and the proper stop after each step, or to pause for 10 seconds after each interval exposure time, with the push of a button. It also allows a and then continue automatically to the next; there is even an photographer to recall any previously stored information from independent time -of-day clock. Seven different audible signals memory. The unit has built-in voltage and temperature stabiliza- can be selected for use with each step. The device is extremely tion and can operate from 117 or 230 VAC, 50/60 Hz. valuable for timing multi -step processes such as making color A device that can be used if you need only to determine prints or developing color film, which involve several chemical exposure times is the Volomat light integrator from Karl Heitz baths and water rinses. (937 Third Avenue, New York, NY 10022), which is a densito- The CT -40 uses a membrane keyboard, something of a meter for black -and -white prints, or for color prints from slides. necessity in the harsh chemical atmosphere of a darkroom where The sensor is a cadmium -sulfide cell, whose output, after strong processing agents can easily ruin a device. The keyboard processing, lights one of a series of LED's. The readings are has luminous markings, which makes it easy to use under accurate to one-third of an f-stop. The 12 LED's correspond to darkroom conditions. A tone is heard each time the micropro- light values from 0 to 2 lux, and the exposure times that can be cessor registers an input. read range from 0.7 -second to 430 seconds. The 4 -digit red -LED display indicates the elapsed time and, Battery powered, the densitometer features a green -LED test when the unit is in the PROGRAM mode, the current sequence - light that also indicates when there is too much light on the easel. step. That provides visual confirmation of the audible sequence A chart on the instrument can be used to determine exposure selected. times for seven different paper grades. In normal use, a light The clock has an accuracy of ±0.5 percent, and timing

43 FIG. 3-THE OMEGA CT-40 DIGITAL TIMER CONTROLLER allows the user to program up to 17 consecutive time intervals. This feature is extremely useful for complex multi -step color -processing procedures.

functions can be entered in either "minutes:seconds" or "seconds:tenths-of-seconds" form. There are two timing ranges: the first covers a range of 0.1 -second to 9 minutes, 99.9

seconds in 0.1 -second steps; the other goes from 1 second to 99

minutes, 99 seconds in 1 -second steps. The timer can be stopped and restarted at any time without affecting the timing sequence. An optional expansion -interface allows the use of preprogrammed plug-in process -control cartridges for automatic operation. Those cartridges automatically program the timer for all popular photographic processes, including Cibachrome, Ektaflex, R-14, and others. A single cartridge can contain information for about 60 steps. The expansion interface also permits the use of additional darkroom accessories: an exposure probe for automatically set- FIG. 4-THE D5500 COLOR ENLARGER SYSTEM is unique in that the ting the correct exposure time, a temperature probe (with read- color head has no user -operable controls-all adjustments are made outs in both Fahrenheit and Centigrade), a digital PH -indicator either automatically or from 3 console keyboard. probe, and others. It also has a built-in self-test program for the CT -40 that checks all 17 program steps, all the digits and indicators, and runs through a 10 -second timing check-all in of the color head (the lamphouse together with its dichroic just 20 seconds. filters) should always be the same. Over time, though, what you An even more sophisticated device is the Omega SCA 400 want may not be what you get, due to lamp aging, the darkening automatic digital color analyzer/timer, which combines both of reflecting surfaces, and other factors. A specially designed color analyzer and timer functions in one microprocessor - quartz -halogen lamp from General Electric helps reduce that controlled unit. problem; the D5500 lamphouse corrects for it by constantly Featuring eight programmable memories, and four -channel monitoring its own color output using a set of three silicon -cell simultaneous digital readout of color filtration and exposure color sensors. time, the analyzer can compute the weighted sum of the yellow, The outputs of those cells are fed to a microprocessor - magenta and cyan filter values and automatically set the expo- controlled circuit that "knows" what the normal color -output sure time. (Of course, if you want, the time can also be set should be and automatically corrects the filtration as needed. manually.) The three dichroic filters, whose positions in the light path The eight memories allow eight different settings for specific determine the color output of the head, are moved to the correct paper/film combinations to be stored in nonvolatile RAM; the positions by separate DC motors in response to the output of the settings are retained when the unit is turned off. Only two color -control circuit. Those motors are also used to introduce the keystrokes are required to access and program the memories. If amount of filtration selected by the photographer for printing; more-or less-light is required from the enlarger, the unit unlike other color heads, that of the D5500 has no external automatically displays the words "LO" or "HI." color -control knobs-everything is controlled electrically or A line of similarly sophisticated solid-state timers and analyz- electronically. ers is also available from Beseler Photo Marketing Co., Inc. (8 The heart of the D5500 system is its auto CLS (Closed Loop Fernwood Rd., Florham Park, NJ 07932). System) controller, which can also be seen in Fig. 4. It connects to the lamphouse, and allows all timing and filter settings to be Enlargers made from one console. Enlargers have gotten very smart, too. One example of how The controller has a backlighted membrane keyboard that is smart is provided by Omega's D5500 enlarger system, shown in used to enter filter and exposure data for the enlarger's color Fig. 4. head. Four 3 -digit LED displays show the filter values and time The system starts with an automatic dichroic lamphouse. selected; the intensity of both the displays and the keyboard Repeatability is extremely important in color printing-when lighting is adjustable. you dial in a certain combination of filter values, the color output Filtration values can be entered from a numeric pad, or

44 program for particular computers. Among the computers supported are the Apple computers, the TRS-80, the IBM PC, and others that use Microsoft BASIC. Another computer -controlled enlarging system is the Fujimo- to G70. Although not as automated as the Omega system, its color analyzer-which is built into its base-allows precise determination of filter requirements and repeatability of results. It is marketed by Colourtronic (9650 Topanga Canyon Place, Chatsworth, CA 91311). The Beseler Dichro 45 system, shown in Fig. 5, uses a microcomputer -controlled dichroic-head color system similar in some respects to Omega's. It, too, checks the quality of the light it outputs. Instead of automatically changing the position of the filters, however, it changes the figures displayed by the 7 - segment LED's that indicate the color makeup of the light inside the head's mixing chamber. A switch allows you to see the actual value of the filter pack, or its effective value. The color head contains a 3870 microprocessor, custom -programmed by the company, that serves as the basic function -controller for the electronics package. Though only about one -quarter -inch square, the microprocessor chip can collect data, make decisions and calculations, and provide output, commands and control signals. Other electronic components in the color head include a quartz -crystal oscillator and nine integrated circuits (including three MOSFET op -amps and three opto -isolators). When the photographer turns on the system, three solid-state photodetectors read the actual color of the light within the mixing chamber of the color head. The particular devices used FIG. 5-BESELER's DICHRO 45 enlarging system is programmable by were chosen because they are extremely sensitive and don't have means of plastic cards with magnetic stripes. the infrared -response problems associated with silicon photodiodes. They also closely match the spectral sensitivity of color photographic-materials. increased or decreased step-by-step by "up/down" keys. Expo- The signals from the detectors are fed into three MOSFET sure times can be entered in two ranges: from 0.1 second to 99.9 operational amplifiers, and from there to a multi -channel seconds (in 0.1 -second increments) or from 100 seconds to 999 analog -to-digital converter. The microcomputer reads and seconds (in 1 -second increments). Whenever the controller restores the data, processes it, and outputs two simultaneous quires informaton to be input, the appropriate key is illuminated signals. The first is a BCD (Binary -Coded Decimal) signal that to call the operator's attention to it. This feature is especially is sent to a BCD -to -decimal decoder which then provides a useful when several steps have to be entered in a particular signal to select the proper LED display. The second signal sequence-the keys will light up one after the other. That makes supplies the display selected with the appropriate information. it difficult to make a mistake. The information is updated every tenth of a second, so that any Two controller models are available. The first is the Auto CLS variation in the color of the light is immediately detected and can Controller just described. The second, the Auto CLS Translator! be corrected for. Controller, offers several additional features. The microprocessor also performs a number of other func- In addition to doing everything its smaller cousin can, the tions, including a self-test diagnostic routine. translator/controller can be connected to a video color -negative Signals to and from the color head can be controlled by what analyzer like those used in high -volume operations, and the Beseler calls its Data Access Timer Analyzer module, or color-correction factors determined using that device will be fed D.A.T.A. The module is connected to the head by a 24 -pin directly to the color head of the enlarger. The translator/ connector. controller also comes with a density probe for making on -easel While the D.A.T.A. module allows you to program the color exposure measurements. head manually, it also has a built-in magnetic -card reader that If desired, the unit can be connected to a color analyzer (like enables it to read data from or write it to a specially designed the CA 400 described earlier), and the output of the analyzer D.A.T.A. card (which looks much like an ordinary credit card). converted directly into signals to control the color head. In The module can store and make use of many types of data, addition, it has a 25 -pin "computer -type" connector, which, including analyzer programs; color -head -memory offsets; Omega says, allows for future interfacing with external memory specific information about a particular negative or slide; and storage -devices, magnetic -card or paper -tape readers, and var- information for automatic variable -contrast control and paper/ ious on- and off-easel densitometric devices. film -emulsion and density control. The translator/controller has 19 program memories and in- With a probe containing three photodetectors, the module can cludes a number of automatic diagnostic features. Among them act as a color analyzer. A timer function lets it address the are a line -frequency check, a temperature check (for the lamp - quartz -crystal oscillator built into the color head, providing an house), and a "high -low" light -intensity check (when the den- enlarging timing capability and exposure repeatability con- sity probe is used). trolled by the on -board microcomputer. A recently introduced option for the system is a parallel It can also perform as a multiple -memory digital color an- computer -interface, which answers the need for computer con- alyzer with a one -button push -to -program feature. Any number trol of laboratory processes. The reason Omega chose a parallel of color-analyzer programs can quickly be stored on D.A.T.A. interface is because its research showed that most of the comput- cards for later use. ers with which its system would be interconnected used a para- As you can see, the nature of the darkroom has changed, llel printer port. The company has solved interface problems thanks to microelectronics. And, since we have progressed this associated with interconnecting parallel ports by using a BASIC far, can the totally automated, computer -controlled darkroom be program and supplying listings that show how to customize the far away? Only time will tell. R -E 45 L J-

L Audio -Frequency

Here's an audio -frequency generator with a digital frequency - readout that is easy to build, align, and use, yet is precise RICHARD SCHROEDER enough for servicing today's sophisticated audio equipment.

IO SAY THAT BOTH HOME AND PROFES- just a "twist of the wrist. - for TTL or CMOS logic work. sional sound installations have become Well, look no further, because the au- One unique feature is a built-in fre- extremely sophisticated would be an un- dio -frequency generator described in this quency counter that continually monitors derstatement. For example, a 1/2 -octave article has all the above -mentioned desir- the output frequency. The device can also band equalizer as well as lowpass and able qualities and a few more. Let's look be wired so that the counter can be used to highpass filters are integral parts of vir- at some of its features and specifications. measure external signals. That frequency tually all professional sound systems. In It has a frequency range of 10 Hz to 50 counter not only allows you to make pre- fact, these days equalizers, tone controls, kHz. That range is continuous, which cise frequency settings, but also elimi- and lowpass and highpass filters are con- eliminates the need for range switching. nates the need for usual large, sidered to be necessary even in home or For increased precision, two controls are cumbersome dial with its myriad of marks auto systems. used to set the frequency. The COARSE and numbers. Generators using that type Today's consumer demands more in the FREQUENCY control is used to set the ap- of frequency "readout" have always been way of performance, which means more proximate frequency while the FINE FRE- difficult for the hobbyist to build and cali- precision is required when servicing au- QUENCY control is used to zero it in brate. dio devices and circuits. Because of that, precisely. The frequency counter itself features old-fashioned frequency generators often The amplitude of the generator's sine - autoranging and a large, four -digit LED prove to be inadequate. Among other wave output is adjustable from 0- to 6 - display. For frequencies up to 9,999 Hz, things, they suffer from inaccurate fre- volts RMS into a high -impedance load or the display reads out in Hz with 1 -Hz quency dials, require range switching, 0- to 3 -volts RMS into a 600 -ohm load. resolution. For higher frequencies, the and often their output level changes as the The device's output impedance is 600 counter automatically switches to the kHz frequency is varied. What we need, then, ohms. The sinewave has a distortion figure mode, which features 10 -Hz resolution. is an audio -frequency generator that has of less than 1% (THD), and its output level You can tell which mode the generator is an accurate output -frequency indicator, a doesn't vary more than a few tenths of a in the by the absence or presence of the "flat" output level as the frequency is dB as the frequency is changed over the decimal point. In the kHz mode, a deci- varied, and one that is free of any range entire range. The unit also boasts a simul- mal point appears after the first two sig- switching, thereby allowing the operator taneous squarewave output with a low nificant digits. to "sweep" the entire audio range with source impedance and a fixed 5 -volt level All of the components except the power

46 R44>+12V R31 1 10K s +12V 1001_8 HF LINIT 4N4.- R7 R1 2.7K 15 71 10012 Q9 11 2N3404 DSP1 I I I I I I 10 R47 COARSE NSB-5881 14 R50 R10 J2 SQUARE- I I I_ I I_ I 10K FREQ. 8.2K 22K D WAVE 11 8 3 13 12 16 Q4 R11 OUT 2N3904 14 = 3302 R2 k12V tO R37- R43 f* LM307 Q1 7 10K Ñ 10052 '" *820# MPF102 D 3 + 7 cc +12V +12V 2 R35 = G C2 ICI R12i$R46 R15 02 1/6 4584 +5V 15 16 17 2 3 4 1110 10µF/ 10K 4 820 2 13 2N3904 IC9 - 4 25V 10 DISTORTION #1 MEG 1 2 74C926 +5V 12 05 -18V R22 5 6 9 13 8 7 2N3904 T R24 R13 i°-EC4 C3 100K /6 4584 1/6 4584 10K 4.7 e R14 121_1 10µF/ 1 R17 6 R34 06 MEG 1,2K 25V 10012 +5V4-4.9"-1 IC 10-c R16 C5 C6 82012 2N3904y +12V +12V +5V R3 = JU1 470K 220pF 200pF R23 10012? +12V R18 R49 (SEE'EXT) 16 100K R6 10K 10 Q3 10K 4.7MEG R45 = SINE AMPL. 2N3904 +5V R33 048 82052 Q7 10K LF351 +12V - C 14 7 10K IC4 +5V 203904 R4 1MEG LF LIMIT R19 = 2 4518 15 7 56052 3 SINE 1/6 4584 11 11 OUT 1 7 FRE- Q. R32 10 FINE R5 +5V 04 1 R25 100K 1/6 4584 pN3904 GNO 1N914 r 2.7K 19 1 J1 l8 10K +5V C =R27, 10K +5V 3 +12V *716 106 D3 01 11 4013 R26 10 14 1N914 1N4002 tOK 12 +5V +5V 6 1405 105 15 Rg 4518 7 1617.810 1N914 10K 18V C10 +5V 1000/ 25V 1_42I7 R30 1/6 4584 = 100K 9 IC7 R23 117VAC 01 47012

FIG. 1-SCHEMATIC DIAGRAM of the audio -frequency generator. If you want to use the built-in frequency counter to measure external signals, jumper all should be replaced with a SPDT switch (see text). and its associated components make up a voltage -to -constant -current converter, the transformer, potentiometers, display, and resistor R3. Depending on the settings of current of which controls the output fre- output connectors mount on a single PC those potentiometers, some voltage will quency of function -generator IC2. The board. The completed project can be be fed to the non -inverting input of op - sinewave output signal from IC2 (pin 2) housed in a small, metal cabinet. amp ICI through resistors R2 and R4. feeds the SINE AMPLITUDE potentiometer, In short, this is an audio -frequency Note that a very small voltage will reach R49, through capacitor C4. Depending generator that provides high-quality per- that same input through R6 in conjunction on the setting of the potentiometer, some formance at a low cost, along with some with trimmer potentiometer R45 (labeled voltage will be fed to the non -inverting unique features. L.F. LIMIT). That arrangement sets the input of op -amp IC3. That op-amp ampli- low-frequency limit of the generator when fies the signal, which How the circuit works is then fed to the the COARSE and FINE FREQUENCY potenti- SINE output binding post through resistor A schematic diagram of the unit is ometers are set to their low -frequency R19. shown in Fig. 1. Let's start with the audio - positions, which, of course, is when both Note that the sinewave signal from IC2 frequency -generator section. Positive wipers are all the way toward ground. also feeds the base of transistor Q2 voltage is applied to the COARSE FRE- Trimmer potentiometer R44, in setting through a jumper wire and capacitor C3. QUENCY potentiometer, R47, through the maximum voltage that is applied to That transistor is configured as an emitter trimmer potentiometer R44 (labeled H.F. R47, in turn sets the generator's high - follower and acts as a buffer between the LIMIT) and resistor R1.. In a similar man- frequency limit when R47 is set to max- audio -frequency generator section and ner, positive voltage is applied to the FINE imum. the frequency -counter section. FREQUENCY potentiometer R48, through Op -amp ICI, along with transistor QI The squarewave output signal from

47 function generator IC2 (pirl 11) feeds the quency to be counted is equal to or greater 10 -Hz signal is also fed to the input (pin 2) base of transistor Q9. That transistor is than 10 kHz. That serves as the detector of divide -by -ten counter IC8. The output configured as an emitter follower and that determines which mode the auto - of that counter (pin 6), with its frequency 1 is serves as a level shifter, buffer, and impe- range system will settle on. The output of of 1 Hz and period of second, also fed dance matcher to provide a squarewave that counter (pin 14, IC5) feeds the input to the resistor/diode system to ultimately level of 5 volts from a low -impedance (pin 3) of flip-flop IC6. That device, and become the timebase for the Hz mode. source at the SQUARE output binding post. its associated components, serves to de- That latter signal is also fed to the reset Trimmer -potentiometer R46 (labeled termine whether 1 -second- or .1 -second - points on IC4, IC5, and IC6. DISTORTION) sets the sinewave distortion period signals from the timebase (to be The regulated DC power supply is to its lowest possible point. The other discussed shortly) ultimately reach the made up of two half-wave rectifiers con- capacitors and resistors associated with latch and reset points on the main four - figured in such a way as to produce both IC2 set its frequency range and sinewave- digit counter, IC9. positive and negative voltages from the amplitude levels. Transistor Q3, ICIO-b, IClO-c, and 12 -volt secondary of power transformer Let's now turn to the frequency -counter their associated components make up TI . The positive voltage is fed to the input section. Sinewave signals from the output pulse generators that supply the latch and of voltage -regulator ICI I, which proof emitter -follower Q2 (actually the junc- reset signals for the four -digit counter, duces at its output a stable 12-volts DC tion of resistors R17 and R18) are fed to IC9. that powers the audio -frequency -genera- 12 DC is fed the input (pin 1) of one of the six Schmitt The circuit composed of ICIO-d, tor section. That same -volts triggers contained in IC10. That stage ICIO-e, Q8, and their associated compo- to the input of voltage -regulator IC12, "squares up" the sinewave signal and nents make up the gated decimal -point - which produces at its output 5 -volts DC, feeds it to the input (pin 12) of the four- drive system. That system works with sig- which powers the frequency -counter sec- digit counter IC9. That IC counts or totals nals from flip-flop IC6 to display a deci- tion. AC power is switched on or off with the squarewave "events," and because the mal point only when the frequency power switch Si. that the frequen- counter is reset at 1- or %t -second inter- counter is in the kHz mode. We mentioned earlier vals, it causes the readout to display in Next we turn to the timebase for the cy counter could also be used to monitor either Hz or kHz. Resistors R37 through frequency counter. AC voltage from the an external signal. That is where jumper R43, along with transistors Q4 through secondary of power transformer TI is fed JUI comes in. Q7 and their associated resistors, make up to the input (pin 9) of Schmitt trigger That jumper should be wired as shown want the the segment and digit -drive system. ICIO-f through resistor R30. That stage on the schematic diagram if you Note that the "squared up" signal that "squares up" the 60 -Hz signal and feeds frequency counter to always measure the feeds the four -digit counter also feeds the it to the input (pin 1) of the divide -by -six output frequency of the generator. If you input (pin 2) of dual decade -counter IC4, counter, IC7. The output of that counter would prefer that the frequency counter be and that IC4's output feeds the input (pin (pin 8), with its frequency of 10 Hz and able to also measure external signals, then 2) of another dual decade -counter, IC5. period of .1 second, is fed to a resistor/ omit the jumper, and wire an SPDT Those four counters connected in cascade diode system that works with flip-flop IC6 switch with its pole connected to the input ter- make up a divide -by-10,000 counter that and transistor Q3 to ultimately become of the frequency counter (the jumper produces an output only when the fre- the timebase for the kHz mode. That same minal that connects to C3). Of the other

6 9/16 INCHES

FIG. 2-ALTHOUGH POINT-TO-POINT wiring could be used, it is recommended that the project be built using the PC board above. That board is shown full-sized.

48 each wire passes through the lug hole with DISP1 the wire being wrapped several times R49 R48 R47 16 15 14 13111 1J1Ú 8 7 4 3 SINE FINE COARSE around the lug and soldered. Be sure that AMPL. FREQ. FREQ. when finally soldering the wires to the PC board that you not only make allowance for the required clearance, but that you ii -R31- I keep that clearance uniform for all three -R38- RI3 1 Q2 D 843 potentiometers so as to have them reason- R40 R 17 RI4 I R21 f R42 -R39- R1 D Q8 Ö ably in line horizontally. Jul 1 R5 R16 1 -R34- Cl2 C4I R14 I I I IR1I In a similar manner, the four -digit dis- -C3- Cl GDQ1 05 -R33- play is supported mechanically by its R44 IR17 J IC9 C17 1C2 -R6-¡' twelve signal wires. The attaching of the R45 IJ I R35 wires is best done by soldering a two- to R46 -J- 1 R8 R13 -C6- three-inch length of bare No. 22 solid I IC7 J J wire to each of the twelve appropriate -R50- I cc 1 JI IC10 1C4 1C12 connectors on the display board. Note that -R10- -R7--R9- CI8 1R21 I I there are 16 total connectors on the dis- -C2-+ -R19-R20I ._ R30I play, but that four of them are not used. As Ç7 O I an aid to getting the wires soldered to the IC11 R11 I 1C8 105 proper points, tape or clamp the display to 01 D2 IC6 IJ _1 your work table with the viewing surface I facing downward and the solder connectors closest to you. The connector on J1 O 1 J2 J3 the left front corner can be considered as GND C connector 16 SQUARE- SINE and the one on the right as - WAVE S1 1. WAVE connector POWER OUTPUT OUTPUT 117VAC Solder wires then to the following connectors: 16, 15, 14, 13, 12, 11, 10, 8, 7, 4, FIG. 3 -THE PARTS -PLACEMENT diagram for the PC board shown in Fig. 2 is shown here. Note that 3, and 1. Be very gentle in soldering and even if you are using perforated construction board and point-to-point wiring it is recommended that handling you follow the layout shown. the display because the foils are very thin and breakable. When all the wires have been attached, bend them two switch contacts, connect one to the clad tips are highly recommended. downward (toward you) with the right- jumper terminal that connects to pin 2 of Use special care to properly install po- angle bends made close to the connectors. IC2; the other switch contact becomes the larized components such as diodes, tran- The display with its attached wires can "external" input terminal. sistors, IC's, and electrolytic capacitors, now be installed on the PC board. Insert because those are very unforgiving when the display wires into the appropriate PC - Construction put in backwards. If you follow the parts - board holes and be sure to hold the display Several methods of construction are placement layout shown in Fig. 3 you level with its horizontal center line about possible. You may choose to mount the should have no problems. an inch above the PC -board surface before components on perforated construction - Although IC sockets are not required, soldering the signal wires into place. board (with .1 inch hole spacing) and use their use is recommended. If nothing else, After soldering, cut off any excess wire. point-to-point wiring. A much better idea it will make servicing and troubleshoot- When choosing your cabinet be sure is to use a PC board. A foil pattern for an ing the instrument easier later on. that it is large enough to accommodate the appropriate board is shown in Fig. 2; a Note several things in regard to mount- board and the off-board components com- parts -placement diagram for the board is ing the three -terminal voltage regulators. fortably. Also, using a vented cabinet is a shown in Fig. 3. If you decide to use The 12 -volt regulator, ICI I, is mounted good idea. perforated construction -board and point- with a 6/32 x 11/2 -inch brass bolt and a'/a- At some point, you will need to drill the to-point wiring, it is recommended that inch hex nut, with the excess bolt length various holes and a rectangular opening in you lay out the components much as they extending upward. The bolt provides a the cabinet for the potentiometers, display are in the PC, board layout to avoid small but adequate heat sink for the volt- bezel, PC -board mounting bolts, trans- ground loops, noise, and other undesira- age regulator. The 5 -volt regulator, IC12, former, etc. Plan ahead and carefully ble characteristics. mounts in a vertical position and it, too, measure everything so that it will all fit If you plan to use a PC board, and will has a brass bolt mounted to it for heat - well. Although most cabinets have a thin be drilling it yourself, you will find that a sinking purposes. The excess bolt length coat of paint when purchased, the drilling No. 60 drill bit works well for all holes should extend toward the rear of the PC process usually puts some nicks and except those for the trimmer potentiome- board. Be sure to install the regulator with scratches in it. Most find that re -painting ters and external wires. For those, a No. its bare -metal side facing the panel - at least the front panel and then applying 55 bit is needed; and, of course, the holes mounted potentiometers (see Fig. 4). press -on lettering gives the instrument a for mounting the three terminal voltage The three panel -mounted potentiome- professional appearance. regulators and the PC -board mounting ters connect to the PC board by means of The PC board is supported about 11/4 holes will require a larger bit, say %s inch. short wires that hold their solder lugs inches above the bottom of the cabinet After the PC board has been drilled, it about is to' inch above the surface of the with four 6/32 x 11/2 -inch bolts. Each bolt should be throughly burnished with steel PC board. That is done to allow the poten- has three 6/-a2 x %a -inch hex nuts attached; wool or very fine sandpaper to remove the tiometers some flexibility, so that when one holds the bolt to the cabinet and the photochemicals and tarnish. That will they are finally tightened against the front other two sandwich the PC board at the definitely contribute to better solder con- panel they will align properly without proper height. nections. All soldering should be done breaking. It would be best to attach those When all the PC -board components with a high -quality rosin-core solder and a wires first to the solder lugs and then have been soldered in place, it's a good pencil -type iron. The newer type metal - solder them to the board. Make sure that idea to thoroughly check the parts place- I I.

PARTS LIST

All resistors 1/4 watt, 5% unless otherwise specified R1, R3, R17, R31, R37-R43-100 ohms R2, R9, R18, R20, R24-R28-10,000 ohms R4, R15-1 megohm R5, R7-2700 ohms R6, R13-4.7 megohms R8, R21-33,000 ohms R10-8200 ohms R11, R12-330 ohms R14-1200 ohms R16-470,000 ohms R19-560 ohms R22, R23, R30, R32-100,000 ohms R29-470 ohms R33-R36--820 ohms R44-R46-10,000 ohms, trimmer potentiometer, upright mount, thumbwheel R47-10,000 ohms, potentiometer, panel mount, audio taper R48, R49-10,000 ohms, potentiometer, panel mount, linear taper R50-2200 ohms Capacitors C1-.01 µF, 100 volts, mylar or polyester FIG. 4-THE COMPLETED BOARD is shown here mounted inside the case. Note the orientation of IC12. C2, C4, C9-10 µF, 25 volts, electrolytic C3, C8-.1 µF, 50 volts, ceramic disc C5, C6-220 pF, 50 volts, ceramic disc C7-.01 µF, 50 volts, ceramic disc the solder connections to be and H.F. LIMIT potentiometers. Rotate the ment, and C10, C11-1000 µF, 25 volts, electrolytic sure all is correct. When that has been COARSE FREQUENCY and FINE FREQUENCY Semiconductors done, it's time to "fire up" the device to controls to their lowest -frequency posi- IC1-LM307 op -amp test and calibrate it. Although that can be tions (fully counter-clockwise) and adjust IC2-XR2206 function generator (Exar) done with the PC board and transformer the L.F. LIMIT potentiometer (R45) for a IC3-LF351 op -amp mounted in the cabinet, it is usually best frequency of 10 Hz. Then, rotate the IC4, IC5, IC8-4518 dual decade counter to at least do the initial testing and calibra- COARSE FREQUENCY control to its highest - IC6-4013 D flip-flop tion with the "electronics" out on the frequency position (fully clockwise) and IC7-7492 divide -by -six counter IC9-74C926 4 -digit counter/driver bench. adjust the H.F. LIMIT potentiometer for a IC10-4584 hex Schmitt trigger frequency of 50 kHz. Check the FINE FRE- Testing and calibration IC11-7812 voltage regulator QUENCY control by rotating it to its ex- IC12-7805 voltage regulator All you will need in the way of calibra- tremes while observing the frequency DSP1-NSB-5881 4 -digit LED display tion equipment is an oscilloscope to change. It should have a total range of Q1-MPF-102 FET check the squarewave and sinewave out- around 500-700 Hz, regardless of where Q2-Q9-2N3904 NPN or equivalent puts. The frequency -limit adjustments, of the COARSE FREQUENCY control is set. D1, D2 -1N4002 course, can be made using the built-in That completes the testing and calibration D3-D5-1N914 frequency counter. procedure. T1 -117 -volt primary, 12- or 12.6-volt sec- Before applying power, set all the trim- If you experience some problems, here ondary, .5 to 1 amp S1-SPST, miniature toggle. to are some troubleshooting hints that may mer and front -panel potentiometers J1-J3-binding posts their approximate mechanical midrange. be helpful: Miscellaneous: PC board, cabinet, dis- Connect the oscilloscope to the sinewave As experience has shown, most prob- play bezel with red filter, knobs, line output and apply power. The oscilloscope lems in home -built instruments are cord, %2 nuts and bolts, etc. should display a sinewave, although it caused by poor solder connections, solder An etched and drilled printed -circuit may be distorted, and the frequency coun- bridges between two adjacent foils, or board is available from: E2VSI, PO Box ter should display the frequency of the components installed backwards. It 72100, Roselle, IL 60172 for $21.00 waveform. Confirm that the frequency would be wise then to first check for those (check or money order) postpaid. Shipping by UPS or best way 3-5 days as COARSE FREQUENCY and troublemakers. changes the after receipt of order. FINE FREQUENCY controls are rotated. Set If you still can't track down the prob- the frequency at approximately 1 kHz and lem, the use of a multimeter is required. adjust the DISTORTION trimmer potenti- With it, check the three major DC power - touch and the same holds true for the main ometer (R46) for a sinewave that looks supply points at various points on the PC four-digit counter IC. So, if the voltages normal on the oscilloscope. If you're a board with respect to the ground foil. The are normal, don't let that be a source of purist you'll need a distortion meter or output side of the 12 -volt regulator (ICI I) concern. spectrum analyzer for that adjustment, should of course measure + 12 volts ± .5 If a problem exists in the frequency - but for most of us, the eyeball method volt, and the output of the 5 -volt regulator counter section, some key points to check works well enough. Next, check the (IC12) should of course measure 5 would be the 60 -Hz, 10 -Hz, and 1 -Hz squarewave using the oscilloscope. It volts ± .25 volts. The negative voltage bus points on the time -base system and also should look the way the name implies and (the negative side of CIl) should measure the squarewave signal that constitutes the have a peak -to -peak value of around five around - 17volts. frequency to be counted. That latter point volts. It should be noted that the voltage reg- can be found at the input of the main four - The next step is to adjust the L.F. LIMIT ulators normally operate quite hot to the digit counter IC9, at pin 12. R -E The Lib and Times of

ASK ANY ELECTRICAL ENGINEERING STU- That was the picture when, in 1884, dent today to tell you something about young Tesla stepped off a ship in New Nikola Tesla, and you are likely to get a York, his head full of ideas, and four blank stare. Or the counter -question: cents in his pocket. His experience had Who was Tesla? It seems preposterous convinced him that the commutator in that our educators should have ignored direct -current motors and dynamos entirely the "father" of our AC age, was an unnecessary complication, but such is the fact. Something should causing endless troubles. He realized be done about our technical educa- that the "DC generator" actually tion system. produced AC, which was converted Born July 9, 1856 in the village of to DC by the commutator. Then, to Smiljan in what is now Yugosla- get that DC to produce rotary mot- via, Tesla rose from relative ion in a motor, the process had to obscurity to a top position in the be reversed. The armature of each scientific world. He became a mil- electric motor was equipped with a lionaire at age 32 through his impor- rotating switch (commutator) that tant inventions, but later faded into changed the polarity of its magnetic obscurity and died nearly penniless. poles just at the right instant as it His father was a clergyman. His rotated to supply AC to the motor. mother, though she never learned to To Tesla, that was sheer non- read and write, was known in the com- sense. It seemed much more logical to munity as an inventor of domestic labor- eliminate the commutator at both gener- saving devices, and it is to her that Tesla ator and motor, and use AC through the attributed much of his inventive genius. whole system. But no one had ever built a The young Tesla, opposing his father's motor that could operate on alternating urging to study for the ministry, insisted current, and Tesla struggled mentally on a career in engineering. His mother tt with the problem. Then one day in Febru- encouraged him. He attended the ary, 1882, while strolling with a class- polytechnic school at Graz (now part of mate named Szigetti in a Budapest park, Austria), specializing in physics and he suddenly blurted out: "I've got it! mathematics, and continued his educa- Now watch me reverse it!" At that mom- tion at the University of Prague. There he ent he had visualized the rotating magnet- took a course in foreign languages so that ic field, which would revolutionize the he would be able to read foreign technical NIKOLA whole electrical industry. He saw the literature. He became proficient in En- magnetic pull racing around the station- glish, French, and Italian, in addition to ary field (statór) of his motor while the German and his native Serbian. armature (rotor), attracted by the moving Finishing at Prague in 1880, he took a field, chased around after it faster and post -graduate course in Budapest, where TESLA faster until it was revolving at the same he debated the merits of alternating cur- rate. He would need no switching to the rent with his professors. He then went to rotating element-no commutator! work for a Paris telephone company, Subsequently he worked the whole where he acquired considerable experi- alternating-current electrical system out ence with DC dynamos and motors. in his mind-including alternators, step- In those early days, direct current was up and step-down transformers for eco- universally acknowledged to be the only Although now largely nomical transmission and delivery of practical medium for generating, trans- forgorten, Nikola Tesla was electric power, and AC motors to supply mitting, and using electricity for heat, either responsible for, or mechanical power. Impressed by the light, or power. But DC resistance losses wealth of available water power going to were so great that a power plant was predicted, much of the waste around the world, he visualized the needed for every square mile served. Ear- technology we now take for harnessing of that great supply with ly incandescent lamps, glowing none too hydro -electric plants capable of distribut- brightly on 110 volts even close to the granted. Here's a look at the ing the power to where it was needed. He power plant, became pitifully dim on the life and achievements of that startled fellow -students in Budapest by power that dribbled from the lines less fascinating man. announcing: "Some day I will harness than a mile away. And everyone believed Niagara Falls." that motors could run only on DC. An The opportunity and fortune Tesla alternating -current motor was considered sought in the promised land did not come an impossibility. easily. When he met Edison, then active- ly engaged in developing a market for his Reprinted from Communication/Navigation incandescent lamp through his pioneer Electronics. E.J. QUINBY Pearl Street plant in New York, Tesla

51 launched with youthful enthusiasm ito a description of his they would have to get a license from Westinghouse if they were alternating -current system. "You are wasting your time on that to keep up with the rapidly expanding electrical industry. The theory," the great man told him, dismissing the idea promptly license-negotiated at a handsome fee-was a feather in Tesla's and finally. cap; he never forgot Edison's statement that there was no future For a year the tall, gaunt Yugoslav struggled to keep from in alternating current and that experimenting with it would be a starving in this strange land. At one point he dug ditches to make waste of time. a living. But the foreman of the Western Union ditch -digging project on which he was working listened to the visionary A dream realized descriptions of new electrical systems that Tesla related during In 1890, the International Niagara Commission began its lunch hours, and introduced him to a company executive named search to find the best way of using the power of Niagara Falls to A.K. Brown. Fascinated by Tesla's vivid plans, Brown and an generate electricity. The scientist Lord Kelvin was appointed associate decided to take a flyer. They put up a limited amount of chairman of the Commission, and immediately announced that a money, with which Tesla set up an experimental laboratory at DC system would obviously be best! It was not easy to challenge 33-35 South Fifth Avenue (now West Broadway). There Tesla that world-famous authority, but Kelvin eventually came to set up a complete demonstration of his system, including gener- realize that if power were to be transmitted even the 26 miles to ator, transformers, transmission line, motors, and lights. He Buffalo, AC would be necessary. Thus, it was decided to use worked tirelessly, and without drawings; the plans for every Tesla's system and generate AC with massive water turbines. detail were indelibly etched in his mind. He even included Bids were invited by the newly formed Cataract Construction two-phase and three-phase systems. Co. in 1893. Westinghouse won the contract for the ten 5000 - Professor W.A. Anthony of Cornell University examined the horsepower hydro -electric generators, and General Electric the new AC system, and promptly announced that ,Tesla's syn- contract for the transmission system. The whole system includ- chronous motor was equal in efficiency to the best DC motors. ing the line and the step-up and step-down transformers followed Tesla's two-phase design. He designed the big alternators Alternating -current arrives with external revolving fields and internal stationary armatures, Tesla attempted to patent his system under a single com- to minimize the weight of the moving members. prehensive patent covering all its components. The Patent That historic project created a sensation, for nothing of that Office would not approve the all -in -one application, insisting on magnitude had been attempted up to that time. The ten big separate applications for each important idea. Tesla's applica- 2250 -volt alternators, revolving at 250 rpm and delivering 1775 tions, filed in November and December of 1887, resulted in the amperes each, produced an output of 50,000 horsepower, or granting of seven U.S. patents in the next six months. In April 37,000 kilowatts, 25 Hz, two-phase. The rotors were 10 feet in 1888, he filed for four more patents, covering his polyphase diameter and 14 feet long (actually, 14 feet high in those vertical system. Those too were promptly granted, as were 18 more U.S. generators) and weighed 34 tons each. The stationary members patents later in the year. Numerous European patents soon weighed 50 tons each. The voltage was stepped up to 22,000 for followed. Such an avalanche of patents, so promptly issued, was transmission. without precedent. But the ideas were so novel-completely absent was any element of interference or "anticipation"-that Remote radio control the patents were issued without a single challenge. Tesla's pioneer work in radio ("wireless" as it was then Meanwhile Tesla staged a spectacular lecture and demonstra- called) went beyond just Morse code communication. In 1898 tion of his AC system-single-phase and polyphase-at a meet- he staged a spectacular demonstration of remote control without ing of the AIEE (now the IEEE) in New York. The engineers of wires at the original Madison Square Garden in New York City. the world were made aware that the limitations on electric - The first annual Electrical Exhibition was then in progress, and power transmission by wire had been removed, opening the door in the center of the vast arena where Barnum and Bailey's circus to tremendous expansion. usually performed he had a large tank built and filled with water. But who would adopt this obviously better system? Certainly Afloat on that small lake he had a 3 -foot iron -hulled boat. Inside not the established Edison -General Electric organization-it the hull was a radio receiver and an assortment of electric would have made their whole investment obsolete. Apparently motors, driven by a storage battery, to perform various ships - Tesla was stuck with no market, no customer for what he had to functions. The receiver's antenna was mounted on the boat's offer. mast. It was at that moment that George Westinghouse walked into From the opposite end of the auditorium, Tesla put the vessel Tesla's laboratory and introduced himself. Tesla was then 32 through a variety of maneuvers, including sailing forward, years old, Westinghouse 42. Both were capable inventors, steering left and right, stopping, reversing, and lighting the accomplished engineers, and electrical enthusiasts. Westing- lights in its rigging in response to audience requests. The im- house listened to Tesla's explanations, watched his demonstra- pressive demonstration of course "stole the show" and made tion, and quickly made up his mind. the front page of the daily newspapers. But how many dreamed "I will give you one million dollars cash for your alternating that one day, using those same radio -remote -servo -control prin- current patents, plus royalties," offered Westinghouse. ciples, we would land a man on the moon? "Make that royalty one dollar per horsepower, and it's a deal," replied Tesla, without apparent excitement. As simply as Mathematical wizardry that, the two men arranged the historic deal and shook hands on Tesla's mathematical genius stood him in good stead in the it. design of the AC equipment for Westinghouse and GE. (In his Tesla had arrived. But he was not a man to forget those who early student days, he solved complex problems in his head, had placed their faith in his ideas, and promptly signed over half without pencil and paper. His teachers suspected him of cheat- his million -dollar fee to Brown and his associate, who had ing, but young Tesla, it turned out, had memorized whole financed his laboratory. Although Westinghouse's backers later logarithmic tables!) The now established frequency of 60 Hz forced him to get a release from Tesla on the dollar -per - stems from Tesla's mental calculations, which convinced him horsepower part of the agreement, such was the friendship that that it was the most practical frequency for commercial use. At had developed between the two men that an amicable settlement higher frequencies, AC motors would become inefficient; at was quickly reached. Tesla relinquished the royalties that would lower frequencies they would require too much iron. Lights have supported him and his research efforts for the rest of his would also flicker at low frequencies. life. Though the original Niagara Falls plant was designed for 25 The phenomenal success of the Westinghouse AC -systems Hz to accommodate the limitations of the early Westinghouse across the nation made it clear to General Electric engineers that turbine generators, subsequent expansion included conversion 52

I le FIG. 1-TESLA AND HIS COILS. Tesla sits in his Colorado research atatlbn while 12 million volts 21 manmade lightning slash around him.

to 60 Hz. Today power from Niagara is transmitted all the way to police station over a block away began to dance around myster- New York City, 360 miles away, and at times is fed over the iously as Tesla confirmed his mathematical theories of reso- Northeast power grid for much greater distances. Remember, nance, vibration, and "natural periods." when Tesla arrived in New York, the limit for efficient power transmission was less than a mile! World's most powerful transmitter Investigations of high -voltage and high -frequency electrical High -frequency pioneering transmission led Tesla to build and operate the world's most During his research in high voltage and high frequency, Tesla powerful radio transmitter on a mountain near Colorado Springs adopted a most sensible practice. When handling high -voltage (see Fig. 2). Around the base of a 200 -foot mast, he built a apparatus, be always kept one hand in his pocket. He insisted 75 -foot diameter air -core transformer. The primary was only a that all his laboratory assistants take that precaution, and to this few turns of wire. The secondary within it was 100 turns, 10 feet day that is always done by sensible experimenters when working in diameter. Using power from a generating station several miles around potentially dangerous high -voltage equipment. away, Tesla created the first man-made lighting. Deafening Tesla's work with high frequencies and in the field of high bolts 100 feet long leaped from the 3 -foot copper ball at the top voltage paved the way for modern electronics, although the of his mast. He was using voltages of the order of 100 million-a word had not yet even been coined. With his unique high - feat not to be equalled for half -a -century. frequency transformers, now called Tesla coils (see Fig. 1). he Tesla burned out the power -plant generator with his first showed that he could actually pass millions of volts harmlessly experiment, but repairing it, continued his experiments until he through his body to glow -tube lamps held in his bare hands.. was able to transmit power without wires for a distance of 26 They would light up to full brilliancy from the high -frequency, miles. At that distance he was able to light a bank of 200 high -voltage currents. In those early days he was actually incandescent lamps-a total of 10 kilowatts. Fritz Lowenstein, demonstrating neon -tube and fluorescent -tube lighting! later to become famous for his own radio patents, witnessed that Tesla's experiments with high and low frequencies some- spectacular accomplishment, as Tesla's assistant on the project. times had unexpected results. Studying slow mechanical vibra- By 1899, Tesla had somehow spent the last of the money he tions, he caused a virtual earthquake in the vicinity of his new got from Westinghouse for his AC patents. Colonel John Jacob laboratory on Houston St. in New York City. His mechanical Astor came to his financial rescue, and put up the necessary oscillator, operating at close to the natural period of the building $30,000 for the Colorado Springs experiments. Now that money itself, threatened to tumble the old structure. Furnishings in a was also gone, and Tesla returned to New York. COPPER SPEIERE, 3' V.A.

NIKOLA TESLA'S 100 MILLION VOLI 'fRANSM17T,,-,

AT COLORADO 5P121NGS, FRITZ L010/[NSTEIN,A551. ENG. 1E99 -VERTICAL CDPPER CONDCCTCR ALONG WOODEN MAST

WOOPEW TOWER

RETRACT RIDLE ROOF EET' ONO

RA,'TER9 A5 PIVI W! DVTT rF, Ef

SECONDA'(Y, 100 Tuft 'O ilr 1 z... ,.44 .i,2 ''.Ay i. 1.1e DIA. r j WO.TSv'n. 1,! =Q- ,IxyltItgi7.1i 1 ,... #' FIG. 2-WORLD'S MOST POWERFUL TRANSMITTER. Using this installa- .. ,itE,.s-. tion, Tesla generated voltages on the order of 100 million, a level not to be :"";,w : ; equalled for nearly half a century. ,+r jE ! r_ Enter J.P. Morgan Fi E' upon by his friend Robert In New York, Tesla was prevailed 1 1 ' 11 Underwood Johnson, editor of Century magazine, to write a feature story describing his accomplishments at Colorado +'\ Springs. But the story Tesla turned out proved to be an involved discourse on the subject of philosophy and "the mechanical `: process of humanity." Although of the highest literary quality, ..._1 the treatise said little about the powerful transmitter at Colorado Springs. Johnson had to return the manuscript three times before getting some coverage of the subject he had requested. In the end, the article was published under the title "The Problem of Increasing Human Energy." It created a sensation when it appeared in print. One of the readers who was deeply impressed was John Pierpont Morgan, who had financed the General Electric Co. in its pioneer DC days, and later in its part in the Niagara Falls project. Morgan was fascinated by the accomplishments, genius of Nikola Tesla, by his spectacular FIG. 3-THE WORLD-WIDE WIRELESS TOWER. Built on Long Island, the and by his winning personality. Tesla soon became a regular mysterious project was never completed. guest at the Morgan home. Impeccably dressed, always the polished gentleman with European manners and cultured speech in several languages, Tesla became a favorite of New York and indebted to the noble generosity of Mr. J. Pierpont Morgan." Newport society. Many prominent matrons regarded him as a From that alliance sprouted the fantastic "world -wide - "good catch" for their daughters, but Tesla insisted that there wireless" tower erected on Long Island; that tower is shown in was no room in his life for women and romance-they would Fig. 3. interfere with his research efforts. Historians differ on what motivated Morgan to finance Tes - World-wide wireless la's next big project. Some believe that he was genuinely in- The strange structure that slowly rose near Wardenclyffe, in terested in the wireless transmission of power. Others argue the hilly portion of Long Island, mystified all observers. Resem- that-in the light of subsequent developments-it seems bling a huge mushroom, except that it was not solid, it had a obvious that Morgan's interest was in getting control of Tesla lattice -work skeleton, broad at the base and tapering toward its and his achievements to protect the Morgan investments in the 200 -foot top. There it was capped by a 100 -foot diameter hemi- electrical industry. sphere. The structure was made of stout wooden members Finding that Tesla was broke again, Morgan agreed to un- joined by copper gussets bolted to the wood with sturdy bronze derwrite Tesla's project of transmitting electric power without bolts. The hemispherical top was draped over its upper surface wires. In 1904, Tesla acknowledged in Electrical World and with copper mesh. There was no ferrous metal in the entire Engineer: "For a large part of the work I have done so far I am structure. FIG. 4-RF ALTERNATORS, such as this first one installed in New Brunswick, NJ, provided the first reliable transatlantic radio communications.

The famous architect Stanford White became so interested in their plant, and that he proposed to use those facilities to distrib- the project that he did the design work without charge, assigning ute 10,000 horsepower at a potential of 10 million volts. one of his best designers, W.D. Crow, to the task. The Niagara project never materialized, but may have had Tesla commuted daily to the construction from his quarters in some influence on the fate of the spectacular Long Island proj- the old Waldorf-Astoria Hotel on 34th St., riding the streetcars ect. For reasons that have never come to light, J.P. Morgan had a to the East 34th St., ferry, then the paddle -wheel steam ferry to change of heart, and Tesla's financial fountain suddenly went Long Island City and the Long Island Railroad to Shoreham. dry. At first Tesla refused to believe that Morgan would not The railroad's dining service prepared special meals for him so arrange for the nearly finished job's completion, but Morgan's that his supervision of the project would not be interrupted. withdrawal was abrupt and final. Historians of the industry When the 100 -foot -square brick power plant was completed wonder why. Did Morgan lose patience? Did engineers of high near the base of the big tower, Tesla began moving his Houston repute convince him that Tesla's visions, so openly revealed in St. laboratory into the structure. Meanwhile, various annoying the brochure, were nonsense, and that he was wasting his money delays were encountered in the manufacture of the radio - on a hopeless dream? Did he suspect that Tesla was diverting frequency generators. Several glassblowers were busy fashion- time and money to the Niagara project? The facts will probably ing special tubes, the design of which remains a mystery to this never be known. Tesla said, however, that Morgan "carried out day. his generous promise to the letter and it would have been most unreasonable to expect from him anything more. " But almost in Tesla's vision the same breath, Tesla said, "I am unwilling to accord to Meanwhile, Tesla issued a descriptive brochure that revealed small-minded and jealous individuals the satisfaction of having his far-reaching insight into the future of the great industry that thwarted my efforts. These men are to me nothing more than at that time (1904) was limited to dot -and -dash telegraphy. That microbes of a nasty disease. My project was retarded by laws of document has persuaded many that the man was actually clair- nature. As for the tower, it was dismantled, although with voyant. He announced that the world-wide wireless system was considerable difficulty, for "security" reasons during World being prepared to provide a variety of facilities, most of which War I. we take for granted today. They included the interconnection of the existing telegraph exchanges all over the world; the es- The radio -frequency alternator tablishment of a secret and non-interferable and non -interfering As early as 1890 Tesla built high -frequency AC generators. government telegraph service; the interconnecion of all tele- One, which had 384 poles, produced a 10-kHz output. He later phone exchanges in the world; a worldwide news distribution produced frequencies as high as 20 kHz. More than a decade was service in connection with the press; a worldwide private com- to pass before Reginald Fessenden developed his RF alternator, munication service, the interconnection of all stock tickers of the which had an output of 50 kilowatts. That machine was scaled world; inexpensive clocks that required no attention yet were up to 200 kilowatts by General Electric, and put on the market as very accurate; the transmission of typed or handwritten char- the Alexanderson alternator, named after the man who had acters; the establishment of a marine navigation system, and supervised the job, and who had built some of Fessenden's more. Much of what he described became reality within his earlier alternators. lifetime. When it appeared that British interests (already in control of most of the world's cables) were about to acquire the patents for Morgan's support ends that machine, the Radio Corporation of America was organized In the Electrical World and Engineer of March, 1904, Tesla at the urgent suggestion of the United States Navy. The new revealed that the Canadian Niagara Power Co. had offered him company was formed in 1919, around the Marconi Wireless inducements to locate his wireless power -transmission project at Telegraph Co. of America, and the powerful but inefficient 57 trans -Atlantic transmitter station WSQ at Marion, Massachu- setts.

Radar and turbines Tesla continued active research in many fields. In 1917 he suggested that distant objects could be detected by sending shortwave impulses to them and picking up the reflected impulses on a fluorescent screen. (If that doesn't describe radar, what does?) He described cosmic rays 20 years before other scientists discovered their existence. At various times up to 1929, he devoted his attention to a "bucketless" high-speed turbine for steam or gas. Friction between the increasingly irascible Tesla and some of those working with him on tests at the Edison Waterside power plant and in the Allis-Chalmers factory did not help his cause, but many respected engineers today agree that we have not heard the last of the Tesla turbines with their smooth rotor discs. As the years passed, less and less was heard from him. Occasionally some reporter or feature writer would look him up and manage to get an interview. His prophecies became increasingly strange and involved, leaning toward the abstract and delving into the occult. He never acquired the habit of writing notes, always claiming (and proving) that he was able to retain complete detailed data on all his research and experiments in his mind. He said that he intended to live to 150, and upon reaching age 100, would write his memoirs, which would include a detailed record of all of the data he had compiled. At his death, during World War II, the contents of his safe were impounded by military authorities, and nothing has been heard since as to what records, if any, were there. One of the peculiar inconsistencies of Tesla's character was revealed when two high honors were offered him, and he re- jected the one but accepted the other. In 1912 it was announced that Nikola Tesla and Thomas A. Edison had been chosen to share the Nobel Prize, including the $40,000 honorarium. Tesla could well have used the $20,000 at the time. Nevertheless, he flatly refused to share an honor with Edison. However, when in 1917 the AIEE's Edison Medal-founded by anonymous friends of Edison-was awarded to Tesla, he was persuaded to accept it, after first refusing.

The esteemed eccentric Tesla's natural demeanor was that of the aristocrat. With the passage of time and depletion of his resources, he sank into a condition of genteel poverty. Continuing to live in the best hotels, his credit would become exhausted and he would be forced to seek other quarters. Finally, moving into the newly opened New Yorker, he found his problems solved. Some of the organizations for which he had made millions arranged with the hotel management to take care of the aging genius. its time. NIAGARA FALLS HYDRO -ELECTRIC power plant, the largest of Tesla insisted on carefully wiping each item of silverware, One of the 5000 -horsepower Niagara Falls units built by Westinghouse. china, and glass before starting a meal, using a fresh napkin for Marconi spark transmitters were replaced by the highly success- each. In view of that effort to achieve perfect sanitation, it seems ful RF alternators. The first one, shown in Fig. 4, was installed inconsistent that the maids reported Tesla's room to be an in New Brunswick, N.J. at station WII. It produced a 200 "unholy mess." It wasn't Tesla's untidiness they complained kilowatt, 21.8 -kHz signal, and handled commercial business about-it was the pigeons! When he was not feeding them out in that previously was transmitted over cable. That was the first the park, he fed them in his room, where he left the window open continuously reliable trans -Atlantic radio service. Those alter- so they could come and go. nators performed so well that a whole battery of them was The gold-plated telephone beside his bed, over which he ordered; they were installed at Radio Central, Rocky Point, could speak to anyone anywhere in the world without charge, Long Island. Ironically, it would have been almost in the sha- was the roost of his favorite pigeon, a white one with grey -tipped dow of Tesla's tower, if that structure had still been standing. wings. "When she dies, I will die," predicted Tesla. And so it Thus Nikola Tesla's world-wide wireless dream was fulfilled was that one day in January 1943, that favored bird paid him her some three decades after he initiated the project, and right where last visit. "She was dying," lamented the lonely, unhappy he started it, using the type of transmitter he devised. Tesla. "I got her message, through the brilliant beam of light One of the giant radio -frequency alternators has been pre- from her eyes." sign served in the Smithsonian Institute. That one originally served at One of the maids, observing that the "Don't Disturb" had been hanging on Tesla doorknob for an unusually long time, used her pass key to investigate. Tesla had passed to his reward, Author's note: I am indebted to the late Hugo Gernsback, friend and leaving his gaunt 87 -year -old frame peacefully in bed. The maid Nikola Tesla; to Prodigal Genius, the biography of Tesla confidant of ushered them out, and closed by John J. O'Neill; to the Proceedings of the A/EE, and to various fed the mourning pigeons, gently publications for their help and information. the window. R -E

I t e

C'QUA ' AM

STEREO

CONVERTER MARTY BERGAN

AM stereo broadcasting is now well under way and more stations are beginning stereo broadcasts every week. Hear for yourself what all the fuss is about by converting your AM radio to receive C-QUAM stereo broadcasts. C-QUAM is a Motorola Registered Trademark

STEREO BROADCASTING BY AM RADIO can be converted to decode stereo. What is C-QUAM? stations was authorized in March, 1982 by Let's say right from the start,' though, C-QUAM is an acronym for Compati- the Federal Communications Commis- that many radios are simply not capable of ble QUadrature Amplitude Modulation. sion (FCC). AM broadcasters hoped that handling stereo. We'll explain the reasons That's certainly a mouthfull-let's see the introduction of stereo would help to for that and we'll explain ways around what it means. The most important word bring back many of the listeners they lost some of the problems. Because AM radi- there is compatible. That means that any to FM radio. If you want to find out what os now on the market were not designed to ordinary (monaural) AM radio can re- AM stereo sounds like, it's easier than you accommodate stereo requirements, you ceive a C-QUAM broadcast and produce think. You don't have to go out and buy might convert a radio but then be disap- the same results as it would if it received a some special receiver-you can convert pointed by the results. We'll give you monaural signal. In other words, the C- your present AM radio to receive stereo some pointers on how to choose a good QUAM system ,does not make standard C-QUAM broadcasts. candidate for conversion. radios obsolete-as is necessary to gain The C-QUAM system, designed by Each of the hundreds of radio designs FCC approval. C-QUAM is a quadrature Motorola, is one of four systems that the will probably behave and sound a little system. That means that it somehow uses FCC authorized for AM stereo broadcast- different. But each radio's problems can the relationship between two periodic ing. (The Commission declined to deter- be resolved with the right know-how and functions that differ in phase by 90°. mine which of several competing test equipment. For those of you who are We'll take a closer look at that shortly. But technologies would become the industry not equipped to handle such problems, let's first say that the final term in the standard and instead took a "wait -and - the stereo conversion may be a disap- acronym indicates that the transmitted see" attitude. In that way. the marketplace pointment, and you might be better off to signal is amplitude -modulated by each of could decide which system would be- wait a few months until the AM stereo the two periodic functions that we just come the standard.) In this article, we will receivers become available in the market- mentioned. take a look at what the C-QUAM system place. But if you want to learn about this A quadrature system combines and is and then we'll look at how an AM radio new system, and you have a good receiver transmits two signals that are 90° out -o1 to start with, then the conversion de- phase with each other. Of course, those -scribet here should 'Linear Applications, Motorola Inc., Semiconductor be accomplished easi- two signals must be separated again at the Products Sector ly anc successfully. receiver, and that's the purpose of this OUTPUT could eliminate that error by multiplying L+R each carrier axis by the cosine of the angle CARRIER AND SIDEBANDS WITH that resulted from the addition of the SIDEBANDS WITH L -R INFORMATION L+R INFORMATION (NO CARRIER) L + R and L -R signals. Figure 2-b shows that when that is done, the result is the 1+ L + R that we want-the standard AM

SUPPRESSED radio sees this signal as the same signal AM TRANSMITTER CARRIER received from a monaural AM broadcast. TRANSMITTER Thus we have complete compatibility. The C-QUAM system adds a 25 -Hz 90° pilot tone to the L -R information at 4% LR modulation that serves several purposes. MASTI-. I; a It signifies that a stereo transmission is OSCILI:1CR present; it permits decoding of the L -R signal, and it aids in control of mono- stereo switching. L+R AUDIO L -R AUDIO

FIG. 1-YOU CAN THINK of a quadrature trans- The MC13020P as made up mitter one actually of two transmit- L+R I he MC 13020P decoder IC is housed ters that are out of phase by 90 . in a 20 -pin, standard dual in -line package, or DIP. A block diagram of the IC is decoder. AM stereo is not the only place shown in Fig. 3. The associated circuitry that quadrature modulation is used. For needed to build a complete decoder is example, color information for TV broad- made up of inexpensive components, casts is transmitted in a similar way. and, in most cases, no coils or adjust- You can think of the quadrature trans- ments are necessary. A schematic of the mitting system as one with two transmit- decoder circuit is shown in Fig. 4. The ters, as shown in Fig. 1. One transmitter is schematic does not show the exact con- a standard AM transmitter at, say, zero LR nection of the C-QUAM decoder circuit phase. It transmits a carrier as well as to the radio to be converted, or an exact sidebands that contain audio information b external -oscillator circuit. But we'll give FIG. 2-QUADRATURE SIGNALS are not di- (the I sidebands). The second details later. transmitter rectly compatible with the detectors used in AM operates 90° out -of-phase with the other. radios. Therefore, they must be converted into Taking an overall look at the block dia- Because a carrier already exists to provide signals that will not produce distortion. gram of the decoder IC (Fig. 3), we see a phase reference for the receiver, we do that the decoder takes the output of the not want another to be generated. So the AM IF amplifier, decodes the C-QUAM second transmitter cancels out the carrier the carrier and the left- and right -channel signal. and provides left- and right -chan- and produces only sidebands (the Q side - audio, or 1+ L + R. That difference or nel audio outputs. In the absence of a bands). Now, since those Q sidebands are error is the cause of the distortion or in- good stereo signal, it will produce an un - generated from a carrier that is 90° out -of- compatibility problem. degraded monaural output from both phase from the original carrier, they are Motorola found, however, that they channels. 90° out -of-phase with the I sidebands. In other words, the I and Q sidebands are in W Q CC quadrature. 5L O 0 0 0 What information do the I and Q side - J,,~j W W w LLI CC CC > F bands contain? The I sidebands contain - O Q the sum of the left- and right -channel au- LL ÿ o dio information, or L+R signals. The Q 1+L+R LEFT Äuizim 7 sidebands contain the difference of the OUT ENVELOPE ERROR LEVEL! ` MATRIX information of the two audio channels, or DETECTOR DETECTOR DETECTOR L -R signals. RIGHT There is a problem with quadrature - 1 /cos OUT modulated signals, though. They produce

VARIABLE I distortion in the envelope detectors of nor- LOCK SWITCH DETECTOR mal AM radios. So a quadrature stereo GAIN system is not compatible with existing 0° 1+L+R radios. That's because the envelope detectors in normal AM radios don't see the I PHASE D L -R PILOT and Q sidebands separately-they see the DETECTOR 4- DETECTOR DECODE a sum of the two, as shown in Fig. 2-a. One 90 vector represents the L + R information INTERNAL that is modulated on the carrier (at what 4-41 VCD PART OF we'll call 0°). The other vector is the The ACTIVE L -R information that's modulated on the BAN D PASS -0 FILTER suppressed carrier (at what we'll call 90°). (25Hz) The magnitude of the sum of those two 10 51 17 '1 F 1.2 vectors-which receiver's the envelope O O O H W Y O /- detector sees-is: QU Q J W Ú Q J 1- co LW d LL ? <1- 0m O ~ = W (1+R+R)2 + (L-R)2. D U Er_ d CO w fN O z O LL However, the envelope detector in a standard AM radio expects to see simply the FIG. 3-A BLOW( DIAGRAM of the MG13020 AM-stereo aecooer IL. provide a constant amplitude of the 25 -Hz C7 C6 LE01 STEREO 11. 2.2µF 10/10V pilot signal at pin It also sends information on signal strength to the pilot de- C2 Z C3 R16" C20 T S R4 i I coder. .1 .0033 .0033 --' ÌC4 l - 100K 330s2 i)- C25 2 0033 I The Q AGC output drives a low-pass i0052 i í005Z 001 ~ T T 10 91 15 filter, made up of a 400 -ohm internal resistor, C18, and R15. From that point, an Ici C9 active filter (made up of both internal and MC13020P 8 1/10V external components) is coupled to the pilot decoder, pin 14, and another low- 19 18 17 16' 11 3 R8 14 Rg 12 RIGHT + 220K 100K pass filter is connected to the co -channel OUT o C19 OSCILLATOR, input, pin 12. C8 v 7.01 LCIRCUIT C15 C14 1/10V +C10 SEE TEXT .47 + .47 2.11 Ó Stereo/mono switching T33/10V 2.7K LEFT TO + A 50% reduction in the level of the 25 - RECEIVER'S OUT «J_ C11 R6 RO Hz pilot signal sent to the pilot -decode IF AMP "inn 150n 9102 C16 OUTPUT circuit will cause the system to go to mon- .4. 4.7µF R14 R12 = R13 aural. A signal at a selected level to the co - 4305. 5.6K 1.6K channel input will also cause the system +Vc . R15 t to go into its monaural mode. +8V -"+C +C17 0 7.5K T 4.7µF18 2.2µF That co -channel input signal contains any low -frequency beat notes caused by interference from a source very close in R18 C22 240 + Cl frequency to the desired signal. The level 100/ CY1 T. í/10V of the input that will cause the pilot -de- T35V R1 T 1.3K "SEE TEXT code circuit to go into monaural can be T,1 adjusted by changing Rl1. The values that are shown in the schematic set the FIG. 4-THE SCHEMATIC OF THE decoder shown here does not show the VCO circuit. "trip" level at about 7% modulation. The pilot decoder has two modes of The first step in decoding the stereo of the same frequency and 90° out of operation. On a strong signal, the decoder information is to convert C-QUAM to phase, the DC output of the detector will will switch to stereo after it sees seven QUAM. That conversion is accomplished be zero. That DC output of the phase consecutive cycles of the 25 -Hz pilot by comparing the outputs of the envelope detector is fed back to the VCO as an error waveform. When conditions are bad, pilot detector and the I (L + R) detector in the signal. Thus, the frequency of the VCO decoder detects the interference and waits error detector. Let's say, for example, that "zeros in" and locks on the input carrier until it sees thirty-seven consecutive cy- the incoming signal is monaural. Then it frequency and we have our phase refer- cles of the 25 -Hz pilot (that takes about consists only of L+R information, and ence to the I and Q demodulators. 1.5 seconds) before it goes into the stereo the envelope detector and I detector see The internal VCO operates at eight mode. (In a frequency -synthesized radio, the same signal. Therefore the error detec- times the IF input frequency. That ensures the logic that mutes the audio during tun- tor does not produce an error signal. that the VCO's frequency is outside the ing can be connected to pin 9 of the de- However, when the incoming signal is AM band, even if the receiver's IF is 262 coder to hold that pin low until the stereo, there will be an error signal pro- kHz. (Typically, a 450 -kHz IF is used synthesizer and decoder have locked onto duced. That's because the envelope detec- with synthesized front ends. But the IF of a new signal.) When pin 9 is held low, the tor sees the same signal as it did before- many auto radios-even if synthesized- decoder is held in its monaural mode and

the sum of the 1 + L + R and L -R sig- is 262.5 kHz.) A 450 -kHz IF places the switches to the short count. nals-because it is not sensitive to the VCO at 3.6 MHz, so you can use an If no pilot is detected for seven con- phase modulation. But the I detector- economic ceramic resonator instead of a secutive counts, it is assumed the incom- because it is sensitive to phase modula- crystal. (See the Parts List.) But, as we ing signal is a monaural station and the

tion-sees only the 1 + L + R informa- mentioned before, the oscillator config- decoder is switched to the long count (37 tion. When both signals are sent to the uration will be discussed later in the text. consecutive cycles of pilot). That reduces error detector, a 1/cos0 correction factor is In the PLL filter at pin 19, ClO is the the possibility that noise or signal -level produced. primary factor setting a loop corner fre- fluctuations will cause stereo triggering. In the variable -gain block, the incom- quency of 8-10 Hz. An internally control- The decoder will also switch to the long ing C-QUAM signal is multiplied by that led fast pull -in is provided. (Pull -in time is count if the PLL is out of lock, or if 1/cosO factor. The resulting product is a the time required for achieving synchro- interference is detected by the co -channel conventional quadrature or QUAM sig- nization in a phase -locked loop.) Resistor detector before seven cycles are counted. nal-not the C-QUAM that is compatible R6 slightly overdamps the control loop, (Each disturbance will reset the counter to with standard AM -radio envelope detec- and C11 prevents high -frequency in- zero.) The level detector will keep the tors. It can be detected (synchronously) stability. The value of CIO can be in- decoder from going into stereo if the IF by conventional means. creased to 68 µF to lower the filter corner input level drops 10 dB, but will not affect The process to detect or demodulate the frequency-that may be necessary to ac- the pilot counter. conventional quadrature signal involves commodate synthesized receivers. It may Once the decoder has entered the stereo first deriving a reference phase from the also be necessary if the filter affects the mode, it will switch instantly back to transmitted signal. That's the purpose of 25 -Hz pilot signal (which must be 0.5 to monaural if either the lock detector at pin the phase -locked -loop (PLL) that we'll 0.7 volts P-P at pin 14.). Resistor R6 may 10 goes low, or if the carrier level drops now describe. The phase detector is a also affect the pilot amplitude, and can be below the preset threshold. Seven con- product detector-its output is equal to decreased slightly if it's necessary to in- secutive counts of no pilot also will cause the product of the two input signal volt- crease the pilot voltage to the required the switch to monaural. ages (in this case, a reference carrier from level. In stereo mode, the co -channel input is the VCO and the QUAM signal from the The level detector senses carrier level disabled. Then, co -channel or other noise variable -gain block). If the two signals are and operates on the Q AGC block to is detected by negative excursions of the I detector. When those excursions reach a ter immunity to tuning disturbances. TO IC1 PIN 18 level caused by about 20% negative mod- However, those types of receivers are not ulation of the L signals, the lock de- guaranteed to be trouble free. Phase mod- R7 -R RES1* 2K tector switches the system to monaural, ulation can originate from the PLL com- even though the PLL may still be locked. parison frequency and may appear as an TO IC1 PIN 17 < Here, the higher tolerance to co -channel audible tone. Extra filtering may be C13" and the 1 C12 other interference prevents chattering needed on the control voltages from 50pF 01 in and out of stereo because of a marginal logic circuits. NPO I signal or high noise -levels (such as during 6. The AGC system of the radio should TO IC1 PIN 16 a thunderstorm). If you wish to decrease be checked to determine that it is effective the effectiveness of the interference sens- enough to control the system gain to "SEE TEXT ing (to keep the decoder in its stereo mode provide a generally constant IF input to FIG. 6 -THE OSCILLATOR CIRCUIT shown here in the presence of some narrow spike type the decoder from all stations. The AGC needs an input IF of 450 kHz. of interference) the 2.2 µF capacitor, C17, should also be slow enough in its response may be increased to as much as 47 µF. so that distortion is not introduced in the to satisfy) all the requirements, the only When all inputs to the pilot -decode 25 -Hz pilot -tone area. In some radios remaining need is to find a suitable DC - block are correct, and the appropriate which use an IC for the AM tuner section, voltage source in the radio to power the (long or short) count is complete, the it is not possible to gain access to the decoder circuit. The source should be switch block is enabled. That block turns AGC'd signals. It is important to test for l l-30 volts when using the on -board reg- on the stereo -indicating LED and passes AGC response after all AGC'd stages. ulator (IC2). Or it should be between 6 the L -R information to the matrix block, 7. A problem with AM tuners using and 12 volts if the on -board regulator is which outputs stereo audio signals. an IC is an IF output voltage that is too not used. The regulator provides about low-often only a few millivolts. In this 8.2 volts to the IC, and its use is recom- Selecting a radio case, a simple, one -transistor amplifier mended. The source must be able to deliv- Not every AM radio can be converted to stage must be added to provide the needed er up to 40 mA continuously. receive broadcasts in stereo. But if you are 200 -350 -mV RMS signal to the de- careful when you examine the radio's ca- coder. Constructing the decoder assembly pabilities, the conversion should go 8. A major advantage is a radio with a Figure 4 shows the complete schematic smoothly. Since there are literally hun- tuned RF amplifier at the front end. The of the AM stereo decoder circuit and Fig. dreds of different radio designs on the increased sensitivity and selectivity aid in market, we can't discuss the details of stereo reception and stability. R5 + R1 converting a particular radio. But we can 9. The IF bandwidth should be at least Vcc f- R18 give you some general pointers: 5 kHz and reasonably flat. The bandwidth C2icz11 Dn1 Ç3 _Rsc11 - -R3 -C2 CjF 1. Old vacuum -tube radios are unac- R- C12 IF IN E I i C4 , IC10 ceptable. You'll undoubtedly have prob- AGC o C19 IC1 lems because of the high voltages and (OPTIONAL) C6 -1 - 71/14---RES1 I -JU LEFT OUT Ctió C13 temperatures involved. C8 2. pocket radios, clock radios, RIGHT OUTo +Cg R9_p8- C16 Cheap -R11- -+R1 small table radios, and the like should not STEREO C7 }R16_R1 Cí8 -R12- be used in most cases. They typically have LED1 /i\ r -R4- -t1,14-+-d.17 narrow bandwidths, poor sensitivity, and ico 0-0 C25 self-generated phase and frequency mod- e\7-1 "SEE TEXT ulations that can seriously degrade chan- FIG. 7-THE PARTS -PLACEMENT diagram nel separation and increase distortion and shown here corresponds to the VCO circuit of noise. (The C-QUAM system uses phase - Fig. 6. Note that C20 is mounted on the foil side related information, so the decoder is sen- of the board. sitive to phase variations or modulation.) 3. Manually tuned radios, whether 5 shows a full-size foil pattern for a single - variable -capacitor or variable -inductor sided printed -circuit board. Before we types, may cause audible microphonics talk about parts -placement, though, we when in stereo mode. (Microphonics are have to select an oscillator circuit. We will electrical noise signals caused by me- 21/8 INCHES 1 discuss three. chanical disturbances of circuit ele- FIG. 5-HERE IS A FULL-SIZE foil diagram of the The requirements of the VCO circuit ments.) Radios with self-contained single-sided decoder board. design are not terribly critical-it must speakers may be subject to microphonic provide a one -volt P-P clean sinewave at 8 problems because of the speaker vibra- times the IF frequency to pin 14 of the tions. Those vibrations may generate of AM radios can vary from 2 kHz to more MC13020P. One circuit that we can use is phase modulation and the associated than 10 kHz. The wider the bandwidth, shown in Fig. 6. The corresponding parts - problems of poor separation, distortion, the better the performance and audio placement diagram for the decoder is and noise. quality. (The fact that so many radios have shown in Fig. 7. 4. The local oscillator must be stable narrow bandwidth has prompted radio Of the three designs we'll discuss, the and produce a reasonably clean sinewave. stations to pre -emphasize the upper audio ceramic oscillator with its matched NPO An unstable oscillator or a severely dis- frequencies-anywhere from 2 kHz on (temperature -compensated) capacitor is torted waveform may cause a fluttering or up-to improve sound quality. Such pre - preferred for its stability and simplicity. warbling in the audio in the stereo mode. emphasis will be reduced in the future as Both the ceramic resonator (RES1) and its Disturbances of the front end and local AM stereo encourages better receiver de- matched (nominally 50 pF) capacitor are oscillator introduce phase noise or ring- signs. available from the source indicated in the ing. You can see that determining whether a parts list. 5. Radios with synthesizer front ends particular radio is suitable for conversion A quartz crystal can be used instead of or logic -controlled varactor tuning are to AM stereo is really the more difficult RES1, but that will result in an extremely best adapted to AM stereo because of the part of the conversion process. Once the narrow pull -in range-only suitable for more precise, automatic tuning, and bet- radio has satisfied (or has been modified stable, accurate digital front ends. The TO ICI PIN 184- TO IC1 PIN 18 -,on`- L2* L1 PARTS LIST 120p Fi RESI* C231 -,- C24 All resistors 1/4 W, 5%, carbon film 39pF IC1 NPO TO PIN 17 « 1N1. R1-1300 ohms TO IC1 PIN 17 4 517 C13" R2, R3-100 ohms C13* 1.5K 1 16pF R4-330 ohms 75pF NPO R5-10 ohms NPO TO IC1 PIN 16 R6-150 ohms TO ICI PIN 16 4-- R7-2000 ohms *SEE TEXT R8-220,000 ohms *SEE TEXT FIG. 8-THIS VCO CIRCUIT can be used if you R9, R16-100,000 ohms FIG. 10 -THIS VCO CIRCUIT can be used to re- need to broaden the tuning area to pull the reso- R10-910 ohms place the ceramic -resonator circuit if your radio nator into lock at the required frequency. (Man- R11-2700 ohms has an IF of 260 or 262.5 kHz. You can also use It ually tuned radios may require that.) R12-5600 ohms with an IF of 450 or 455 kHz if you change the R13-1600 ohms value of C13. R14-430 ohms ceramic resonator permits a much broader R15-7500 ohms pull -in range, but it does have two draw- R17-1500 ohms backs. The available resonator oscillates R18-240 ohms better tolerance and small size. But regu- at 3.6 MHz-that requires a 450 -kHz IF Capacitors lar electrolytics, if accurate, can be used input to the decoder. Radios with a 455 - C1,C8,C9-1 µF, 10 Volts, electrolytic with no sacrifice of performance. Non - kHz IF will have to be re -aligned. The C2,C3,C4,C11-O.0033 µF, ceramic disc, polarized capacitors may be ceramic -disc 25-50 second drawback concerns manually volts types unless otherwise specified in the C5-0.001 µF ceramic tuned radios. Tuning to the station's cen- disc, 25-50 volts parts list. The 0.1-µF capacitor, C6-10 µF, 10 volts, electrolytic C20- ter frequency is quite critical. (That's not shown in C7, C17-2.2 µF, 10 volts, tantalum Fig. 4 connected from IC1 pin 6 likely a to be problem with synthesized C10-33 µF, 10 volts, electrolytic to ground-should be soldered on the cir- tuners.) To broaden the tuning area, R7 is C12,C19,C25-0.01 µF ceramic disc, cuit side of the PC board under the IC added to lower the Q of the VCO. Capaci- 25-50 volts from pin 6 (Vcc) to pin 16 (ground); use tor Cl2 provides a DC block. C13-NPO. See Text and Figs. 6, 8, and short leads when installing that unit. Note If greater broadening is needed, LI and 10 that there is intentionally no provision for RI7 may be added, and C13 changed, as C14,C15-0.47 µF, 10 volts, tantalum this capacitor in the board layout. shown in Fig. 8. (The corresponding C16,C18-4.7 µF, 10 volts, tantalum C20,C21,C24-0.1 µF parts -placement diagram is shown in Fig. ceramic disc or Converting the radio monolythic 9.) That aids the circuit in pulling the The input signal to the must be C22-100 µF, 35 volts, electrolytic decoder at resonator into lock at the required fre- C23-see text and Fig. 10 least 160 mV RMS for stereo. But for quency. If LI and R17 are not used, each Semiconductors and other compo- quiet, clean reception, it should be must be replaced with a jumper wire as nents 200-350 mV. That is a typical range for shown. IC1-MC1302OP C-QUAM decoder most AM radios. In the radio, the stereo If your radio does not readily tolerate (Motorola) decoder goes where the detector would re -alignment, or if it has an IF of 260 or IC2-LM317LZ adjustable regulator normally go-after the last IF stage before 262.5 -kHz, or if you prefer not to attempt LED1-standard red LED, 20 mA the detector diode. The radio's detector L1-120 µH choke re -alignment, an alternative VCO, using a circuit may be disconnected by removing L2-55 µH coil: 60 turns of #36 enam- tunable L-C oscillator circuit, is shown in the diode or disconnecting one lead. In elled wire tightly wound on Y8 -inch di- Fig. 10. It replaces the ceramic -resonator ameter form with No. 2 ferrite core and some radios, AGC voltages are obtained circuit and is very stable. The coil must be shield can. from the detector circuit and, in that case, tuned so that the oscillator frequency is 8 RES1-Ceramic resonator, Murata the detector should be left connected. In times the radio's IF frequency. The circuit CSA2.60MT7 with matching capacitor most instances it won't interfere with the shown accommodates the 260 -262.5 -kHz (C13), Murata CSC500K7 operation of the decoder. In any case, the IF range. Coil L2 is an adjustable RF coil The following are available from Cir- audio output from the radio's detector made up of 60 turns of No. 36 enamelled cuit Specialists, Box 3047, Scottsdale, must be disconnected, to avoid conflict AZ 85257: Complete kit, including PC wire tightly wound on a V8 -inch -diameter with the two audio channels coming from board and all parts (including parts for form with a No. 2 ferrite core, a pot core the MC13O20P. the VCO circuit as in Fig. 6 only), (ferrite shield) and a shield can. $24.95; Circuit board only, $4.95; Ce- The decoder assembly may be mounted ramic resonator RES1 with matching in any convenient place, but try to keep it NPO capacitor (as in Fig. 6) only, $3; MC1320P decoder IC, $3.50. All prices -R5- R1 R6 include postage inside the US. Vcc 4- + -RS- R1 R6 C1 1- \ 22/R311 D01 C3 Ich -«---k22/C211 R18 I Dal - C19_R2_ _C21C12 i. C3+C1 1C11 IF IN4 ti -C4 IC10 ' C19_R3 =C21C12 AGC O - L1 IFIN4 I C4 IC10 IC1 You can use the circuit in Fig. 10 (it's 1r (OPTIONAL) C6-' RES1 AGC o + C5- parts -placement is shown in Fig. 11) with (OPTIONAL) C6-+ IC1 C231 L1 LEFT OUT i ,í0% R9 1C13 C14 an IF of 450 or 455 kHz by C13 LEFT OUT C5- R9C24 to RIGHT making 39 o +' -R8 C16 R10 -R12 pF NPO and C23 10 pF NPO, and adjust- RIGHT OUTo+ 8 R8 +C16 STEREO C7 ±R16 + + IR11=R10- R15- R13- ing L2 so that the oscillator's center fre- STEREO C9--6-R15+ LED1 -R4-R4-JpR14 C7 -R 6_ R12 +C17 quency is eight times the input IF. LEDI(l R+ C17 l R4 15 R14 6( C18 5 C15 Except, perhaps, for some of the os- C25 cillator parts, the components required for C18 C15 *SEE TEXT %/ C14 the decoder circuit are common parts. We FIG. 9-THIS PARTS-PLACEMENT diagram cor- *SEE TEXT responds VCO 8. recommend that you use tantalum capaci- to the circuit shown in Fig. FIG. 11 -THE PARTS tors for the -PLACEMENT diagram Capacitor C20 is the only component mounted polarized capacitors in the shown here corresponds to the VCO circuit of on the board's foil side. filter circuits at IC pins 10-14. They have Fig. 10. away from major heat sources such as a power transformer, output transistors, and WHERE TO LISTEN heat sinks. If the interconnecting wires are more As we went to press, these stations (listed alphabetically by city) were broadcasting C-QUAM stereo, with almost 50 orders on backlog. (Those stations wished to remain confidential.) than a couple of inches in length, or if they will power-supply components pass near KRZY 1450 Albuquerque, NM CKNW 980 New Westminster, BC or wires, then you should use shielded WSAN 1470 Allentown, PA KXXY 1340 Oklahoma City, OK cable. Connect the cable shields to WCHL 1360 Chapel Hill, NC CJSB 540 Ottawa, ONT ground at one end only. The ground return WAIT 820 Chicago, IL KGW 620 Portland, OR wire from the decoder assembly should be WFAA 570 Dallas, TX CJCI 620 Prince George, BC connected to the radio's ground bus at the WJR 760 Detroit, MI WHWH 1350 Princeton, NJ radio's IF output or detector circuit. To KQWB 1550 Fargo, ND KIPN 1350 Pueblo, CO avoid ground loops, this should be the WKQT 1010 Garyville, LA KKLS 920 Rapid City, SD WGSW 1350 KKYX Antonio, TX only common ground connection. Greenwood, SC 680 San CKOC 1150 Hamilton, ONT KFMB 760 San Diego, CA has a high IF output (over If the receiver WIRE 1430 Indianapolis, IN KYA 1260 San Fransisco, CA 350 mV RMS) a series resistor can be WNDE 1260 Indianapolis, IN KRDZ 1230 Steam Boat Springs, CO added to drop the voltage to the desired CKOV 630 Kelowna, BC KJOY 1280 Stockton, CA level of 200-350 mV RMS at pin 3, the WITL 1010 Lansing, MI CFRB 1010 Toronto, ONT decoder input. The input impedance of CFPL 980 London, ONT KRMG 740 Tulsa, OK the decoder is about 27 kilohms. KFI 640 Los Angeles, CA CJVB 1470 Vancouver, BC Pin 9 of the IC is the FORCED MONO KZLA 1540 Los Angeles, CA CKWX 1130 Vancouver, BC control pin. Grounding that pin locks the WISM 1480 Madison, WI CKLW 800 Windsor, ONT WSM 650 Nashville, TN decoder in its monaural mode. For automatic mono/stereo switching, pin 9 can be pulled up with a 100-kilohm resistor to 2. Pin 17-The VCO input. The os- Proven conversions the 8 -volt supply (as shown in the schema- cillator input should be a sinewave In preparation of this article, three radi- 1 P -P 8 times the tic), or it can be connected to pin 10. (That of about -volt at os were converted in our lab. The first was input IF. permits the most rapid re -acquisition of an AM (dnly) portable radio, a Realistic 3. Pins 7 and 8-The left and right retuning.) If you look closely stereo after audio outputs. These signals (Radio Shack) model 12-656A. (It is not at the parts -placement diagrams, you'll should typically be about 200 mV listed in Radio Shack's latest catalog.) notice that, although the jumper is not P-P, centered on a DC level of That radio was chosen because it has an shown, pads are provided on the board so about 1 volt. FET-tuned RF amplifier in front, no ce- that you can easily tie pin 9 to pin 10. You 4. Pin 14-Pilot tone. You should see ramic filters, (they usually narrow the could also bring pin 9 out to a switch and a 25 -Hz sinewave that is steady bandwidth), three tuned IF stages, and a manually force the decoder to its mon- and 0.5-0.8 volts P-P. The ampli- substantial AGC system. Our testing tude can be increased, if neces- aural mode by switching pin 9 to ground. showed that its 3 -dB bandwidth was 12 sary, by decreasing the value of If that is the case, the 100K resistor must kHz with a very flat response. One AGC R12 (but to no less than 1.8K). The sure to remember: Do be added. But be pilot signal will be present, of voltage is developed from the detector cir- 9 not add the resistor if you jumper pins course, only if the radio is properly cuit, so the detector was left connected as and 10. tuned to a station transmitting C- is. The IF was re -aligned to 450 kHz. The The left and right audio outputs are QUAM stereo. speaker and battery holder were removed "tuner-level" signals (100-200 mV 5. Pin 1-L+R signal. This signal to make room for the decoder circuit and a RMS) and can be connected directly to looks like the audio signals on pin complete 4 -watt -per -channel stereo am- the tuner or auxiliary inputs of a stereo 7 and 8 but it is centered on a DC plifier with volume, balance, bass, and amplifier. If the conversion is in an AM/ level of about 6 volts. treble controls. The radio's original audio 6. Pin 20-L-R signal. This should FM receiver, one that has its own stereo section was disconnected. The radio lent appear about the same as L + R amplifier, the decoder outputs should be signal. (If you observe closely, you itself readily to the conversion with only connected through the band switch. Ca- should also see the 25 -Hz pilot one problem. As previously discussed, pacitors C8 and C9 will provide the neces- tone as a low -amplitude compo- manually tuned radios often prove to be sary AC coupling to the audio circuits. nent of the complex waveform.) microphonic. The 12-656A was no excep- 7. Pin 10-DC lock voltage. The volt- tion. The main culprit was the oscillator Troubleshooting age should be 4 volts in lock, 0 volt coil. Filling the coil assembly with If the decoder will not go into the stereo out of lock. If it's out of lock, the beeswax to stop vibration greatly im- not at 8 times the input IF. mode even with a strong signal, then you VCO is proved it. The tuning capacitor also was Adjust the VCO or re -align the ra- should troubleshoot the circuit as we'll sensitive, but no attempt was made to Of course, before you start trou- dio's IF. describe. 8. Pin 9 -FORCED MONO. If wired to suppress it because of the possibility of bleshooting, you have to know that the pin 10, it must have the same volt- damage. Even so, at this point it took a local radio station is transmitting age condition as pin 10. If not wired substantial rap on the cabinet to get a little Motorola C-QUAM stereo-feel free to to pin 10, pin 9 must have + 4 V DC "ping" sound. The radio was connected call the station to be sure. or higher via a 100k pull-up resis- to a pair of Radio Shack's Minimus -3.5 When you're certain that a C-QUAM tor (R16) to the 8 V supply. If the speakers that presented a full, clean stereo signal is being received, (we'll assume voltage at pin 9 is at or near 0 V sound with both laboratory equipment as is held in mon- that you've checked that the power supply DC, the decoder the C-QUAM signal source and a com- aural mode. is working correctly and that 8 volts DC is mercial radio station in Chicago. supplied to pin 6) then, using an oscillo- The second radio converted was a Sears scope, look at the following signals: If all the above conditions are satisfied, model 564.50800, a car radio with digi- 1. Pin 3-The input signal. The signal the decoder will switch into the stereo tally controlled varactor tuning, FM ster- the IF output envelope (and that at mode. Failure at this point indicates a eo, and an 8 -track tape player. The unit receiver) should show modu- of the workmanship problem, defective compo- presented a different challenge because of lation at the top and bottom edges or an its compact assembly and complexity. symmetrically. The average ampli- nent, a fault in the receiver system, that is not correct for C- The selected frequency is digitally dis- tude must be 1 volt peak -to -peak, incoming signal ± 0.4 volt. QUAM stereo detection. continued on page 128 EST QUIPMENT A look at what's new what's sophisticated, and what's unusual in test equipment today

ELECTRONIC TEST EQUIPMENT PRE THE POTS AND PANS OF AN only test equipment they need, own or use. To others it's a scope, electronics ab. Without the meters, scopes, generators and all or a function generator, or an RF signal generator. Most of us the offer devices we use to measure, examine ani regulate the have used a cigi:al multimeter, scope, generator. and various electronic equipment that surrounds us in today's world we component testers. But have you ever used a logic analyzer; a would soon drown in a very maze of beautiful and sophisticated, network analyzer; or a portable oscilloscope that has a liquid - but inoperative electronics hardware. crystal display and also sports a memory? These are just some of Bu: what is test equipment? The answer to that simple ques- the very sophisticated and unusual electronic test equipment that tion is complicated. It depends on who you am an:: what you do. can be found in labs around the world. Let's take a look at some ,some, a multimeter is test ectemenL In fact. it may be the of these special ietruments. LCD digital storage scope multimeter On the front cover of this issue is one of the most fascinating pieces of test equipment that I have seen lately. It's a simple portable oscilloscope. But that's where the simple ends and the exciting new technology begins. Note the liquid -crystal display and the memory. Take a measurement, carry the instrument away and the measurement is still there in the scope's memory. The M 2050 from BBC Metrawatt is a unique combination of a low -frequency digital oscilloscope, a 31/2 digit multimeter and a transient recorder with two independent memories tucked into one neat portable package. An expensive oscilloscope if you compare it to conventional equipment, but if you look at the kinds of special jobs it can perform you will soon agree that the price is fully justified. If there is any disadvantage to the unit it is in its frequency range. Because of the limitations imposed by the display, top frequency is 50 kHz. The price of this unit is $1795. First take a look at how small this instrument is-a mere 257mm x 169mm x 88mm when folded, and it weighs only 1.95 kg. Since the display is an LCD device it draws very little power and the battery -powered unit runs other battery-powered NEW FLAT-PANEL OSCILLOSCOPE, model M 2050, from BBC-Metrawatt/ the functions of a digital oscilloscope, a 31-digit multi- Thanks to the memory you can capture a Goerz combines scopes into the ground. meter, and a transient recorder into a single, portable Instrument. waveform while working in a cramped corner, then walk away and examine that pattern and compare it with the ones in your lyzers are powerful measurement tools for today's complex digi- service data later. All -in -all a great example of what technology tal systems. They are essential during the critical phase of can do. integrating hardware and software. Costly design errors can be When using the instrument, measurements can be evaluated avoided. more accurately because the scope and multimeter operate si- When digital products are in production or operational, a logic multaneously. For example, while the scope portion of the dis- analyzer is the instrument that quickly isolates a problem and play is used to evaluate signal characteristics, the DMM portion decreases downtime. In a new line of logic analyzers recently can be used to display the true RMS value of the signal. Because introduced by Racal -Dana a new dimension is added to this the inputs were designed with the voltage- and current -handling instrument's capability-a fast, easy -to -use, effective software characteristics of a digital multimeter in mind, the Digital Scope debugging tool. The model 205, an example of a top -of-the -line Multimeter can be used directly for high-voltage measurements. instrument, is priced at $6995. It offers 48 channels of state Up to 500 volts can be applied to the 200 -mV range without analysis and 16 channels of waveform plus many significant damaging the instrument. On all other voltage ranges 780 -volt features, including a 16 -channel word generator, 12K bytes of overload protection is provided. non-volatile memory and a GPIB (General Purpose Interface Operating as a scope, the M 2050 digitizes analog signals at a Bus) interface. A more detailed discussion of the GPIB appears 500 kHz rate. At 10 samples per cycle, the effective bandwidth is later in this article. 50 kHz. The transient recording capability of the instrument Applications for logic analyzers are not limited to the labora- enables the operator to use two independent 0.5K x 8 -bit tory. Data and information gathered by using these instruments memories to record data. It can capture events as brief as 2 ms. during design and development does not have to be put up on a Once recorded, data from either memory can be recalled and shelf leaving the people in production, testing, quality control, displayed for analysis. Waveforms can be retained in memory for and service to rediscover facts already known. With good plan- months. An analog output makes it possible to make a hard copy ning and design, physical connections and simple routines for of the data when connected to a strip recorder. logic analyzers can be built right into the equipment the instrument has helped to design. This will provide for quick trou- Logic analyzer bleshooting and efficient maintenance even after the product is in As stated in the latest Hewlett-Packard catalog, logic ana - use.

FULL -FEATURED LOGIC ANALYZER from Racal -Dana offers 48 channels of state analysis and 16 channels of waveform. The interface standard. model 205 also includes a 16 -channel word generator, 12K bytes of non-volatile memory and a GPIB di üíf i..FogMI irmaimain1 I reef! airMationimpag NEW LINE OF DIGITAL MULTIMETERS, the 70 Series from Fluke, intro- PROPAGATION DELAY CAN BE MEASURED ACCURATELY with the HP duces some significant changes in DMM technology. The bar pattern 1726A time -interval oscilloscope. In this photo a 10 -inch length of semi- across the bottom of the digital display is an analog display that greatly rigid coax cable has a delay of -1.43 ns. The minus sign indicates that the enhances the capabilites of the instruments. channel A signal occurs later than the channel b signal.

Digital multimeters Time -interval oscilloscope If you want to look at extremes, here are two instruments, both Offering 50 -picosecond accuracy and 10 -picosecond resolu- with the same name, but each at opposite ends of the DMM tion the new Hewlett Packard HP 1726 scope makes fast, reliable spectrum. The John Fluke Manufacturing Company is a major timing measurements on complex repetitive signals. The instru- manufacturer of digital multimeters. At the top end of the spec- ment combines counter and oscilloscope technologies. It has the trum they produce their model 8506A, a unit that they claim viewing and measuring capabilities of a 275 -MHz scope and the delivers performance at the edge of technology. I must agree. ease of use of a time -interval counter. That is particularly useful This instrument has 71/2 digits of resolution, a 24 -hour accuracy to those making frequent timing measurements. of 120 -parts -per million from 40 Hz to 20 kHz and a stability of Designed to make precise timing measurements, the HP 1726 30 parts -per -million. The instrument's top notch accuracy is uses a crystal -referenced time base in conjunction with a CRT attributed to the use of a thermal-RMS detection technique based and stable triggering circuits. This combination makes it possi- on the heat dissipated by a resistor. As a result the instrument's ble for the instrument to display the signal being tested as well as response is relatively independent of the input signal's waveform to measure the designated interval with up to 50-picosecond and full accuracy can be guaranteed for a wide range of input accuracy. At $7,675, the HP 1726 is far from cheap, but for the signals. high-technology and high-performance portion of the elec- The only problem with this instrument is that it represents tronics industry it meets the requirement found in fundamental drastic overkill for most digital-multimeter applications. It's a lot areas of research -and -development labs, production, and ser- like hiring a Greyhound bus to take one person from place to vice. As a diagnostic tool the unit is excellent for characterizing place instead of using a taxi. designs, processes and entire test systems. At the other end of the spectrum is Fluke's newest and least expensive digital multimeters, a line of three instruments in the Digital module tester 70 Series. Starting at $85 and packed with a variety of high- The most advanced automatic test equipment technology in a priced features, including an analog liquid -crystal display for compact 28 -pound package is the way Bendix introduces its reading peaks, I think that this meter represents a new standard model 9070 digital module tester. The primary purpose of this for the test -equipment industry and fortells the future of portable- instrument is to separate bad circuit -card assemblies from good multimeter technology. For more details on this instrument see ones. It can handle GO/NOGG screening and fault isolation the Equipment Report elsewhere in this issue. diagnostics on everything from a simple circuit card to a complex system. It works in the field, on the bench, or on the production Synthesized signal generator line. The highly sophisticated instrument tells the operator what Over its entire range of 80 kHz to 520 MHz, all you need do is to do-step by step; it signals when a fault is detected and punch out the frequency, the modulation and the RF level of the displays test results instantly. desired signal on the front -panel keyboard and you have it at the In the field, the portability of the 9070 makes it possible to output. Designed by Marconi Instruments to test transmitters take the tester to the problem and find the fault there. This does and transceivers, frequency resolution is within 10 Hz at all away with board swapping and cuts down on the number of frequencies. RF output up to + 13 dBm is available at all fre- boards in the service pipeline. Good boards stay on the job. quencies and microprocessor control provides operating Obviously this is not used in simple systems or where the boards simplicity and speeds up routine measurements. A non-volatile being tested are relatively inexpensive. In those instances, sim- memory stores' up to 10 generator settings and a further 40 ple board swapping is more efficient and less expensive. At the carrier -frequency values. The memory also stores calibration repair shop the unit finds faults that need repair in bad boards information. Microprocessor-aided fault diagnosis lets the user, quickly and automatically, delivering the kind of quick turn- from the front panel of the instrument, pinpoint the section of around and throughput that is needed for an efficient shop testing this instrument that is not functioning properly. operation. .

The Universal Disturbance Analyzer is specifically designed for use in the computer field -service industry and continuous on - site monitoring of computer operations. Voltage disturbances are printed out in industry -standard terms of sags, surges, and impulses (including impulse duration). In addition, the 626 will have applications in the analysis of power problems associated with telecommunications systems, industrial process -control systems, medical instrumentation and, of course, the entire range of microprocessor -based equipment. Testing cellular-radio receivers What do you use to test these state-of-the-art receivers? Boon- ton Electronics says try their model 1021 programmable RF signal generator. It has a frequency range to 1.08 GHz and covers all of the requirements for high-speed testing of cellular receivers. Switching time between channels is 50 ms. Output levels to + 16 dBm, SSB noise of less than -113 dBm, residual FM below 12 Hz at 900 MHz, and FM distortion of 0.05%. In DIGITAL MODULE TESTER does Its loo Dy applying input signais modulation oscillator can responses at designated addition, the low-distortion, internal, designated input pins and certifying predicted and output pins. This tester is the Bendix Model 9070. be used as an audio oscillator with programmable frequency level. The generator can be controlled manually, automatic via GPIB, or preset to recall up to 250 complete panel setups from an memory. Oh, about the price.... a mere To do its job the 9070 applies input signals at designated input integral non-volatile pins and verifies predicted responses at designated output pins. $16,950. Any sequence or combination of the following input signals may be used for each individual test: Input logic pattern Change of state at one pin or simultaneous change of state at multiple pins Sequential change of state at selected pins Single or multiple clock pulses at individual or group of pins Output response may be verified by any of the following methods: Full output go pattern Change in output at single or multiple pins from prior test Specific logic level at single or multiple pins Maximum system capability is 256 active input/output pins. All pins are programmable; no dedicated adapter is required. Universal disturbance analyzer Anomolies on the AC power lines can affect computers and other senisitive microprocessor-based instruments. To counter this problem is the Dranetz Technologies Series 626-Universal Disturbance Analyzer. This is a modular, portable microprocessor-based instrument made up of a mainframe and up to five individual plug-in modules. By choosing the appropriate plug -ins the user can monitor single-phase AC, 3 -phase AC, DC IF YOU'RE SERVICING CELLULAR RADIO equipment, a programmable RF voltages, common -mode AC voltages, and logic event changes - signal generator like the Boonton Electronics model 1021 is what you of-state. need. The special feature is that it covers the requirements for high-speed testing of cellular receivers.

Component and circuit tester The TR -I Tracer from Non -Linear Systems is not an expensive instrument, but it is a fascinating one because of the wide range of tests it will perform. How does one describe it? Well it is an in -circuit and out -of-circuit tester of components and net- works. Signature analysis patterns provide the key to rapid fault finding. The unit tests all parameters simultaneously of circuit boards or individual components without power -up. Dual inputs make it snap to compare a known good component with a suspect. When testing equipment the TR -I locates shorts, opens, and wrong parts in a minimum of time. Since the unit works equally well in or out -of-circuit it can also be used in receiving inspec- tion for qualitatively checking a variety of components. Because the unit conducts dynamic testing rather than static testing it can detect faulty parts suffering from defects such as noise leakage, temperature instability and intermittent deficiencies that might TOGETHER WITH SOME OF ITS INPUT MODULES is the Series 626 Univer- go undetected using other methods. You are sure to find many This unit can spot and record sal Disturbance Analyzer from Dranetz. additional applications for this device. Battery powered and anomalies that affect computers and other sensitive microprocessor - based instruments. easily portable, it's a handy companion in the field.

68 INCREMATIC DC VOLTAGE/CURRENT portable calibration standard allows unlimited use of any one decade with full borrow/carry to and from all more significant digits. This instrument is the model 8200 from Data Precision.

IN-CIRCUIT OR OUT -OF -CIRCUIT the Non -Linear Systems Tracer checks the output in decimal values.) The desired values appear above out and troubleshoots circuits, subassemblies and components rapidly the rotary switches and accurately. All tests can be performed without powering -up the circuit displayed on a set of LED's. The unusual being checked. lncrematic Control Feature enables the operator, using any one rotary switch to control not only that particular decade, but all of the successive significant digits. Thus external instruments can be exercised down to any reso- Inexpensive frequency counter lution, step after step, using only one knob for a particular test- Not all good things must be expensive. Here's a frequency run resolution. This feature is extremely useful when measuring counter than ranges from 5 Hz to 1 GHz, yet costs only $575. It's linearity of D/A and A/D converters, as well as the transfer the Global Specialties model 6002. It also measures period from function and linearity of analog function modules such as multi- 1 µS to 200 ms. Also, there are three selectable resolutions with pliers and dividers. LED indicators and simple push-button control. A 10 -MHz crystal oven oscillator time -base assures ± 0.5 ppm, ± 1 ppm/ year stability. Arbitrary waveform generator The unit is intended for use for audio/VHF in communica- So you want to generate custom waveforms. The Wavetek tions, data processing, process control, RF design, digital de- model 175 will do that job for you. It lets you tailor your own sign, quality control, and maintenance. There's an 81/2 -digit waveform. Any waveform that can be drawn can be entered into display featuring leading -zero blanking, 0.43 -inch tall charac- this versatile instrument and then generated as an output. ters and a contrast -enhancement filter. This unusual device stores waveforms as digital points on a 256 x 255 data grid. These points are sampled by a crystal - controlled clock at selectable times up to 200 nanoseconds. Amplitude can be varied a full 20 volts peak -to -peak with 3 -digit resolution. Waveform shape data is entered in any one of four 6000FREOUENCYCOUN7ER Lee MRfNlN 4 RAM memories through the front -panel keyboard or the GPIB. MACAW I' f.] 111:1 IJ cW Yo,etr You enter the data for each change -of-slope location and the internal microprocessor connects these points. In addition, plug- ... in sockets are provided for four PROM's so you can create a . comeo,,,.Á;,.-/ permanent library of your most used waveforms. One place that IMO this instrument is invaluable is in medical electronics where we can create the many irregular waveforms that are often required. ARE 81/ DIGITS ENOUGH in a frequency -counter display? The model 6000 frequency counter from Global Specialties provides that display of the frequencies it measures.

Calibration standard if> w.-_ DC voltage/current portable calibration standard that's NBS ,s7411»tairee .r . (National Bureau of Standards) traceable is a handy instrument to have around. And the Data Precision model 8200 delivers higher effective resolution, higher stability, exceptional accuracy and great flexibility in a unique new way. This instrument is an extremely accurate microcomputer -based, remotely programmable, line -powered portable standard for the transfer of NBS reference values to instrumentation and equipment in a broad range of working environments-in the lab, in the quality -accep- tance quality -control department, and on the production floor. When operating in the manual mode, the 8200's 6 -digit control network is controlled by setting its associated rotary switches to any reading between 000000 and 1048575 plus polarity indication, with appropriate decimal point location. (The inter- THE MODEL SS -5711D four -input, eight -trace, portable oscilloscope from nal microcomputer translates from binary to BCD, so you read Iwatsu. It also features a digital multimeter. MANUFACTURER LIST BBC-MetrawatVGoerz Dranetz Engineering Labs Marconi Instruments Ct. 6901 West 117 Avenue 1000 New Durham Road 100 Stonehurst Broomfield, CO 80020 Edison, NJ 08817 Northville, NJ 07647 Nicolet Instrument Corp. Bendix Corporation John Fluke Manufacturing Co. 5225 Verona Rd. Test Systems Division PO Box C9090 Madison, WI 53711 Teterboro, NJ 07608 Everett, WA 98206 Non -Linear Systems 533 Stevens Avenue B&K Precision Global Specialties Corp. Solana Beaach, CA 92075 6460 West Cortland Street 70 Fulton Tr. Chicago, IL 60635 PO Box 1942 Racal -Dana New Haven, CT 06509 4 Goodyear St. PO Box C-19541 Boonton Electronics Irvine, CA 92713 499 Pomeroy Rd. Hewlett-Packard Parsippany, NJ 07054 3000 Hanover St. Tektronix Palo Alto, CA 94304 PO Box 1700 Beaverton, OR 97075 Data Precision Corp. Elect Avenue Iwatsu Instruments Wavetek Inc. Danvers Indl Pk 120 Commerce Rd. 9045 Balboa Avenue Danvers, MA 01923 Carlstadt, NJ 07072 San Deigo, CA 92123

THIS RACK -MOUNT oscilloscope, the 3901 from Nicolet, features a digital readout and a bubble memory for storage.

NTSC Color -Bar Generator GPIB compatability in With all the attention that video gets these days, thanks to the The General Purpose Interface Bus (GPIB) was established VCR, videodisc player and video cameras, a good NTSC gener- 1975. Three years later, in 1978 the IEEE standard defining this system that has ator is increasingly valuable. One moderately-priced, yet quality bus was further refined, defining an interfacing standard. The unit is the model 1250 made by B&K. It is a cost-effective unit become a widely accepted instrument industry for broadcast, CATV, and industrial television applications. It's major areas it specifies are: also useful for aligning and troubleshooting VCR's. Mechanical-the interface connector and cable. logic signal levels and how the signals are sent This unit accurately generates the standard NTSC bar pattern Electrical-the received. the lower quarter of the pattern as and with an IWQ signal occupying Functional-the tasks an instrument's interface may perform a five -step well as the full -screen color-bar pattern. There's also (such as sending data, receiving data, triggering the in- staircase pattern with selectable chroma levels. Dot, cross- strument) and the protocols to be used. -cross patterns, and color raster are also hatch, dot -hatch, center Today, a wide variety of instruments include interfaces con- available. forming to this mechanical, electrical and functional standard. Fiber-optic cable tester With GPIB compatibility, measurement capability can be chosen bus cables in With the importance of fiber-optic cables in electronic com- off-the -shelf and simply cabled with standard munications constantly growing an electronic device to test these either a linear or star configuration. cables was sure to be close behind. Enter the Tektronix OF150 Some closing comments Fiber Optic TDR. This high-performance, easy to use instru- excit- ment performs repeatable, accurate distance and loss measure- Obviously an article of this nature cannot include every every man- ments on multi -mode optical cables. Typical applications ing new instrument, nor can we possibly mention think that the include: splice measurement though a one-way cable loss of up ufacturer of quality test equipment. Please don't in this article are the to 21.5 dB within ±0.1 dB; detection of fiber ends though a one instruments and manufacturers mentioned new instruments are way cable loss of up to 42.5 dB; and measuring distance to only ones that we have seen. Scores of each month and what we have tried to do here is bring discontinuities to 19.9 km, with 1 -meter resolution. announced interesting The OM150 delivers direct LCD readout of results. A built-in you a sampling and cross-section of those that have R -E chart recorder provides a permanent record of the waveform. and sometimes different features. 70 CD) 0

Solid State BAROMETER Measuring and charting the atmospheric pressure has long been recognized as an effective way to make weather forecasts. Now you can build this state-of-the- art barometer and make your own weather predictions.

SUDHIR K. GUPTA

BEFORE WEATHER SATELLITES CAME INTO SENSOR CAVITY use, the barometer was perhaps the most SIGNAL useful instrument for providing informa- CONDITIONER 3/16 -INCH tion about future changes in the weather. 1 Both mercury and aneroid barometers 13181NCH PRESSUREBRASS have long been used to measure the at- PORT DIFFUSED 1_ SENSOR mospheric pressure. But we're going to ELEMENT 42!64 -INCH show you PRESSURE a new type of barometer-a TRANSDUCER barometer that uses a state-of-the-art sol- MEASUREMENT AND id-state pressure transducer and gives a 6.9 VD I DISPLAY STRESS digital readout of atmospheric pressure. POWER RELIEF The barometer that we'll build can be MOUNT SUPPLY 5VDC thought of as being made up of four basic building blocks. As shown in Fig. 1, they FIG. 1-THE SOLID-STATE BAROMETER can be a include the pressure transducer, power thought of as being made up of four blocks of circuitry. GROUND supply, signal conditioner, and the mea- v surement -and -display section. Let's look at each separately. 7 The pressure transducer v, 6 2 A transducer is a device which trans- 5 4 forms one form of energy to a different V2 form of energy. In this barometer, we'll be using a pressure transducer that converts b barometric pressure into electrical signals. The transducer is made by SenSym (1255 Reamwood Ave, Sunnyvale. CA 94809) and is shown in Fig. 2. It is an absolute -pressure device. That is, it measures pressure relative to a vacuum. (An- other pressure -transducer type is the gage type, which measures pressure relative to ambient pressure.) The transducer's sensing circuitry is deposited on a silicon chip that has a cav- c ity etched out to form a diaphragm. On the FIG. 2-THE LX0503A pressure transducer is FIG. 3-THE STRUCTURE of the LX0503A is top of the diaphragm (the "exposed" ideal for barometric applications. shown in a and its pinout is shown in b. The schematic of the device is shown in c. We will side) is the pressure -sensing circuitry. The not use the VT pin, which is normally used for other side of the diaphragm is a vacuum. resistance of the piezoresistive elements temperature compensation. Figure 3 shows the structure of the device changes as the pressure changes, and thus along with the transducer's pinout and its the output voltage changes. The voltage pressure. schematic. on pin 6 (V1) increases with an increase in The signal -conditioner section is nec- Changes in ambient pressure affect the pressure. The voltage on pin 5 (V2) de- essary to provide zero and offset correc- deflection of the sensing diaphragm. The creases (or goes negative) with increasing tions for the transducer output. The signal

71 from the transducer (about 40 millivolts) +5V is amplified to about 1 volt. That corresponds to a display of 100 kilopascals (ab- R5 Ry R6 220K 10K breviated kPa). We'll discuss that unit, 100K VV and others, shortly. IC2 to LM329 We want the power -supply section R2 13 3 2 10K provide + 5 volts DC for the signal -con- 5 2 o VO UT 2 ditioning and measurement section as IC5 (TO LX0503A well as 6.9 volts DC for transducer excita- 3 1/4 LM324 R7 METER) 1/4 LM324 tion. Therefore we can use an AC adapter R3 g 4.7K R1 10K that provides 8 -11 volts DC. Such adapt- 1K SR4 ers are readily available from many ? 220K The sources, including Radio Shack. -5V adapter's output is filtered and regulated +5V +5V by IC3, a 7805 5 -volt regulator. A monolithic voltage converter, IC4 (an ICL7660 from Intersil) provides -5 volts DC. Fi- nally, a Zener diode is used to provide 6.9 volts DC to the transducer. The measurement-and -display section is based on a single -IC A/D converter -5V from Intersil: their ICL7106. The author's FIG. 4-A ZENER DIODE is used to regulate the transducer's input voltage to 6.9 volts. prototype used Intersil's 1CL7106 EV panel -meter evaluation kit for a display. It is capable of displaying 199.9 millivolts or 1.999 volts full-scale. In our applica- IC3 +5V tion, the full-scale reading is set to 1.999 8-11 VDC rt- µA78M05

volts. C C2 I C3 Circuit description 1 1µF/25V ^.1 8 Conventionally, the pressure trans- TANTALUM is by a 10 -volt DC IC4 o 5V ducer powered -15 ICL7660 power supply, and a 6.9 -volt Zener diode C5 is shunted across the supply terminals 2 4 I 10/25V (pins 3 and 8). That provides an excitation + TANTALUM voltage of 6.9 volts DC. Unfortunately, C4 when that is done, there is a common - 10/25V o GND TANTALUM mode voltage of about 1.8 volt DC at the signal -output terminals (pins 5 and 6). We is easily converted to a bipolar supply by using the ICL7660 do not want the small transducer output FIG. 5-THE POSITIVE 5 -volt supply voltage converter. signal of 30 - 40 millivolts to ride on such a large common -mode signal.

To get around that problem, we can fled by ICl-c to about 1 volt. That gives us good idea. However, that's not necessarily either use an expensive instrumentation a scaling factor of 10 millivolts per kilo - so. The pascal is the standard unit for amplifier with large common -mode rejec- pascal. pressure or stress in the International Sys- tion ratio (CMRR), or we can play a trick. tem of Units (SI). ANSI (the American That is, we can use a bipolar supply of i- 5 Scaling the display National Standards Institute) has adopted volts DC instead of a 10 -15 volt DC Barometric pressure is expressed in a the pascal as its standard pressure unit. It supply. As shown in Fig. 4, we can con- variety of units, including pounds -per- is equal to one newton per square meter nect pin 3 directly to + 5 volts DC and we square -inch (psi), bars, millibars, pas- (N/m2). Weather reports often give baro- can connect pin 8 through a dropping re- cals, inches of mercury, atmospheres, metric readings in millibars as well as in sistor to -5 volts DC. (We can obtain the ton, etc. Table 1 is a conversion chart to inches of mercury just as they give tem- -5 volts from the ICL7660 that we dis- help you convert from one unit to another. perature readings in both Fahrenheit and cussed earlier; the power -supply sche- To use that chart, look across the top for Celsius. Conversion from kilopascals to matic is shown in Fig. 5. The ICL7660, the unit you want to convert from then millibars is simply a matter of multiplying incidentally, is listed in this year's Radio look down the side for the unit you want to by a factor of 10. catalog.) A precision Zener refer- convert to. Multiply the units you have by Shack Construction ence across pins 3 and 8 regulates the the conversion factor indicated by the ta- the voltage to 6.9 volts DC. That technique ble, and your answer will be in the units The project is built in two parts; reduces the common -mode voltage to a you want. transducer/power-supply board, and the for a mere 100 millivolts. Now it is feasible to Because we are using a 31/2 -digit dis- display board. A suggested layout is shown use a conventional op -amp (like the play, the maximum resolution is obtained printed -circuit transducer board diagram is LM324) as a differential amplifier. when the pressure is displayed in kilo - in Fig. 6. A parts -placement not really One quarter of that quad op -amp (ICI - pascals (millibar/10) or millibars. A baro- shown in Fig. 7. However, it's as a) is used as a differential amplifier. It metric scale of 95 kilopascal (28 inches of necessary to use a PC board. It is just amplifies the input signal by a factor of mercury) to 105 kilopascal (31 inches of well to use perforated construction board about 22. We use ICI -b, another section mercury) more than covers the useful and point-to-point wiring. We do, of the LM324 quad op -amp to introduce barometric pressure range. You may think however, recommend that you use IC the offset that will be required to calibrate that using the unit of pascal (a unit that sockets for all IC's. the barometer. The signal is further ampli - you've probably never heard of) is not a As we mentioned before, the display

72 PARTS LIST

All resitors 1/4 watt, 5% unless otherwise noted R1-1000 ohms R2,R3,R6-10,000 ohms R4,R5-220,000 ohms R7-4700 ohms R8,R9-100,000 ohms, multiturn trimmer potentiometer Capacitors C1,C3-0.1 µF, ceramic disc. C2-1 µF, 25 volts, tantalum C4,C5-10 µF, 25 volts, tantalum Semiconductors IC1-LM324 quad op -amp. IC2-LM329 6.9 -volt precision voltage reference IC3-µA78M05 5 -volt regulator (Fair- child) or similar 1C4-ICL7660 voltage converter (Intersil) IC5-LX0503A pressure transducer (SenSym) Miscellaneous: IC sockets PC or perforated construction board, Intersil evaluation board ICL 7106 EV kit or any meter with a 2 -volt range, AC adapter, 8 -11 volts DC section of the author's prototype is based upon an evaluation board from Intersil- their 1CL 7106 EV kit. That was used as a 4 1/2 INCHES dedicated display. If you want to avoid the expense of that kit (about $35), you can FIG. 6 -FOIL PATTERN for the barometer is shown full-size above. The layout is not critical, and point- use an ordinary digital voltmeter or even to-point wiring can be used -but be sure to use a socket for the transducer. an analog meter with a full-scale range of 2 volts DC. If you do use the Intersil evaluation should, however, have no problem power- Apply 8 - 1 l volts DC to the trans- board, follow the instructions that are sup- ing the display. ducer/power-supply board and check for plied with it to set the full-scale display to As we mentioned before, the use of IC ±5 volts DC at the output indicated in the 2.000 volts. Keep in mind that there is no sockets is strongly recommended. The parts -placement diagram of Fig. 7. Also need to use a battery to power the ICL7106 pressure transducer can be installed in an check for 6.9 volts DC at the transducer EV-the transducer/power-supply board eight -pin socket. But don't install it-or socket. Bend the transducer pins, recheck generates ± 5 volts that can be used for any IC's -yet. First install all resistors, the orientation, turn off the power, and powering the display board. Connect +5 capacitors, potentiometers, and IC sock- install it in the socket. 1f you wish, you volts to the v + input on the evaluation ets. Check for solder bridges and clean all may install the transducer remotely and board and -5 volts to the v - input. We of the flux off the board. If you used point- connect it to the transducer board through should note here that the current drain to-point wiring, be especially careful of a four -wire shielded cable. from the + 5 -volt supply should be lim- cold -solder joints. When you have dou- You can mount the unit in just about ited to a few milliamps. Otherwise, degra- ble-checked your work, you can install all any cabinet, but you should keep the dation of -5 -volt supply will result. You the IC's except the transducer. transducer outside the cabinet, or make

TABLE 1 -CONVERSION FACTORS

PSI PASCAL kPa MILLIBAR in.Hg mm Hg ATM TORR

PSI 1 1.4504 x 10-4 0.1450 1.4504 x 10-2 0.49118 1.9337 x 10-2 14.696 1.9337 X 10-2

PASCAL 6.8946 x 103 1 1000 .100 3.3865 x 103 133.32 1.0132 x 105 133.32

kPa 6.8946 1 x 103 1 10 3.3865 0.13332 1.0132 x 102 0.13332

MILLIBAR 68.946 1 x 10-2 10 1 33.865 1.3332 1.0132 x 103 1.3332

in.Hg 2.0359 2.9529 x 10-4 0.2953 2.9529 x 10-2 1 3.9368 x 10-2 29.920 3.9368 x 10-2 mm Hg 51.714 7.5006 x 10-3 7.5006 0.75006 25.401 1 760.00 1

ATM 6.8045 x 10-2 9.8692 x 10-6 9.8692 x 10-3 9.8692 x 10-4 3.3422 x 10-2 1.3158 x 10-3 1 1.3158 x 10-3

TORR 51.714 7.5006 x 10-3 7.5006 0.75006 24.401 1 760 1 VOUT How to use your barometer to O predict the weather.

Although some of you will build this barometer simply because you enjoy building electronic projects, many more will actually want to use it to predict the weather. So that you can do that, here's a crash course on what barometric -pres- IC2 sure changes usually mean. bring fair R6 R7 High-pressure cells generally IC5 ICI weather. In the northern hemisphere, the air circulation is clockwise and winds are usually light. The temperature can be warm or cold, but will remain constant for J relatively long periods of time. Low-pressure cells generally bring R8 I I I I cloudy weather, with rain or snow. In the R1 R5 R4 R2 R3 northern hemisphere, the air circulation is

I I I I counter clockwise, and winds are usually strong. Tropical lows are warm, but other lows are cold, or change to cold. A steady barometer usually indicates unchanging weather for one or two days. Any rapid fall usually indicates that rain or unsettled weather is on it's way. (A rapid IC3 IC5 C4 rise or fall in barometric pressure is gener- IC3 ally considered to be 0.05 to 0.09 inches C1 C2 (0.16-0.30 kPa) over 3 hours.) The lower the pressure before the rapid change, the sooner the rain will approach. For example, if the pressure is 29.8 inches (100.9 kPa) and falling rapidly, a severe storm wll pass within a few hours. A rapid rise signals that the storm is ending, and clear and colder weather is on its way. A suggestion to make the barometer more useful is to inteface it with a computer (such as the control computer that con- cludes with Part 3 in this month's issue). -5V +5V GND Then you could automatically chart the 8-11VDC changes in pressure and record the highs and lows that occur. We'd like to hear FIG. 7-THE PARTS -PLACEMENT diagram for the foil pattern shown in Fig. 6. about your successes (and failures).

sure that your cabinet is not -tight fitting. gle -point calibration is to adjust potenti- course, M, - M1 = 1030 - 972 mV = The best place to mount the unit is in an ometer R9 until the meter displays the 58 mV. old aneroid barometer. Then you not only barometric pressure. The generated slope is OM/AP or have an interesting conversation piece, If you can, it is best to use two -point (M, - MI)/(P, - P1) = 58/4.5 mV/kPa or but you can also use the old barometer's calibration. That's because a typical trans- 12.88 mV/kPa. pressure scale as a conversion scale! ducer requires an offset correction as well The slope that we require is 10 my/kPa. as slope correction. Therefore, the change in the gain required Transducer calibration As a first step, perform the single -point is 10/12.88 = 0.776. A typical transducer requires a two - calibration that we just discussed and What we are going to do is to reduce the point calibration to correct for offset and leave the unit operating over a period of a gain generated by the op -amp by a factor gain over the entire operating range. In the few days. Try to obtain two readings: one of 0.776. An example of how to do that case of this barometer, the actual operat- at the low end of the scale (around 98 kPa) follows. ing range is limited to ± 5% of the top of and the other at the high end of the scale Measure the voltage at the output of the scale (95 -105 kPa). Therefore, a sin- (around 102 -104 kPa). On both those ICI -a. We'll call it V;. Presume that V1 = gle -point calibration performed at the days, note the actual barometric pressure 755 millivolts. Then the gain of ICI -c = middle of the range (100 kPa) may be as well as the corresponding meter read- M2/Vi = 1030/755. The required gain, acceptable. So that we can please every- ings. We'll use a little mathematics to however, is 1030/755 x 0.776 = 1.059. one, we'll discuss both methods. arrive at the calibration values. Following So the required output at ICI -c is 1.059 X Before doing any calibration, switch are some sample calibrations. Vi = 1.059 x 755 = 799 mV. the unit on and let it warm up for about an Let the old barometric pressure, P1 = Adjust the gain potentiometer, R9, un- hour. Set potentiometer R8 to its middle 98 kPa and the corresponding meter read- til the meter reads 799. Now adjust the position. Obtain the barometric pressure ing, M1 = 972 mV. offset potentiometer, R8 until the meter (using the local weather forcast or a ba- Let the present barometric pressure, P2 reads 1025 millivolts, corresponding to rometer that you know to be accurate). = 102.5 kPa and the present meter read- the present barometric pressure. That Using Table 1, convert the barometer's ing, M, = 1030 mV. completes the calibration. Now you can reading to kilopascals or millibars. (The The change in barometric pressure is P. substitute your own values in the calcula- closer the reading is to 100 kilopascals, - P1 = 102.5 - 98 kPa = 4.5 kPa tions and perform the calibration on your the better.) All that is to be done for sin- The change in the meter reading is, of digital barometer. R -E

74 111

How to Design MANNIE HOROWITZ Power Supplies

All about unregulated and regulated power supplies, IC regulators, and overvoltage- flows through it. protection circuits. The polarity of the voltage across the transformer is reversed during the negative half-cycle. Now, the bottom terminal of the transformer is positive with respect IN THIS, THE FINAL INSTALLMENT IN OUR T1 to ground and with respect to the top ter- 01 series, we will turn our attention to power minal. Diode D1 ceases to conduct be- supplies for analog circuits. All circuits cause its cathode is more positive than its require some source of power to operate anode. But as for D2, its anode is now 1' ;VAC and the most convenient source of such !RL positive with respect to its cathode and the power is an AC wall outlet. Unfortunately, 02 device conducts. Thus, current flows from many electronic circuits cannot make use N the lower terminal of the transformer, of AC directly. Instead, some way to con- through D2 and RL, and back to ground vert the AC to DC is required. FIG. --A SIMPLE full -wave rectifier using a cen- and the center tap, and a positive half- Let's look once again at the junction ter -taped transformer. cycle of voltage is developed across RL. diode. You will recall that in our previous Note that here, once again, the voltage discussions of that device we saw that it from an AC supply have some ripple. across RL varies identically with the input only conducts when its anode is positive Using a battery is not always possible or waveform, but the polarity of the voltage with respect to its cathode. That property practical, but fortunately most circuits across the resistor is reversed-it is posi- is important when we are dealing with can tolerate the presence of ripple if it is tive. AC. If the diode were connected in a se- sufficiently attenutated. That sequence repeats during the suc- ries circuit along with an AC supply and a One way to minimize ripple is to use a ceeding positive and negative half-cycles. load, its presence would mean that current full -wave rectifier. Such a circuit is shown Note that current always flows through RL could only flow through the load during in Fig. 1-a. Note that the circuit consists of in the same direction so that only a posi- the half of the AC cycle when the anode a center tapped transformer, with the tap tive voltage with respect to ground is was positive with respect to the cathode. grounded, and two diodes. Let's see how across the load. That is true regardless of During the other half cycle the diode this circuit works. We'll start by looking the instantaneous polarities of the AC would not conduct and no current could at what happens during the positive half- voltage applied to the circuit. flow. cycle. During that half-cycle the polarity The advantage of the full -wave rectifier Such an arrangement is referred to as a of the applied voltage is such that the over the half-wave rectifier lies in the fact half-wave rectifier because only half the upper terminal of the transformer's sec- that in the half -wave circuit no voltage is waveform (i.e. alternate half-cycles) is al- ondary is positive with respect to the cen- developed across the load during negative lowed to pass freely. The other half of the ter tap and the lower terminal. Also, half-cycles. Because of that, the ripple in waveform is cut off. during that half-cycle the polarity across the output of the half -wave rectifier is The presence of those half-cycles of DI is such that the anode of the diode is higher. current causes pulsating DC to be gener- positive with respect to its cathode and the For ripple to be minimized in either ated across the load. The amount of volt- device conducts. Thus, current flows from type of circuit, some type of filtering must age variation in that pulsating DC can be the upper transformer terminal, through be used. To do so, a large capacitor is reduced by wiring a "filter" capacitor Dl and RL, and back to the center tap usually placed across RL. That capacitor across the load. The amount of ripple in through the ground. Note that the voltage is charged to the peak voltage, V , , dur- the output is then determined by the val- during this half-cycle varies in phase from ing the first half-cycle. Between peaks, it ues of the capacitor and the load. 0° to 180° and that the current varies from discharges slowly through RL. But it does zero, to some peak value, and then back to not have enough time to discharge sub- Full -wave rectifiers zero. Because of that varying current, the stantially before the next half-cycle ap- When dealing with electronic circuits voltage developed across RL varies identi- pears and recharges it. such as amplifiers, the power source cally with the input waveform. Finally, Without the capacitor, the ripple volt- should be as stable (i.e. free of ripple) as during the positive half-cycle the cathode age across RL varies from + Vp to 0 volts. possible. The ideal power source then is a of D2 is more positive than its anode, so But with the capacitor present, it varies battery, as all DC voltages that are derived the diode does not conduct and no current from + V P to whatever its voltage

75 dropped to before the next half-cycle ap- circuit, the output, or DC voltage across peared to recharge it. From that, you the load, is determined by the peak volt- should be able to see why the ripple is age across the secondary of the trans- easier to filter in a full -wave rectifer. The former (or across one-half the secondary reason is that the filter capacitor is re- of a center -tapped transformer if a full - charged once during each half -cycle in a wave rectifier is being used). Should one full -wave circuit, while in the half-wave of the previously described rectifiers be arrangement it is recharged only once dur- used without a transformer between it and ing each Because this longer the voltage source, the DC voltage at its full cycle. of a recharge cycle, the voltage across the ca- output seems to be limited to the peak pacitor drops to a lower level. The ripple voltage of the AC source. But a voltage - voltage, the voltage variation from +Vp doubler circuit can be used to increase the to that discharge voltage level, is therefore level of the rectified DC. Two circuits larger for the half-wave than the full -wave involving doublers are shown in Fig. 3. circuit. In the circuit shown in Fig. 3-a, Cl is In both circuits, the amount of ripple at charged to the peak level of the supply the output is related to the values of the voltage through D1 during the positive FIG. 4-TWO OR MORE voltage doublers can be filter capacitor and the load resistor. For a half-cycle. On the negative half-cycle, C2 combined to form voltage tripiers, such as the full -wave circuit, ripple will be kept with- is charged through D2 to the same peak one shown in a, or a voltage quadrupler, such as in reasonable limits if the product of the level. Since the series combination of the the one shown in b. values of the load resistor and the filter two capacitors is across the load, the volt- capacitor is about 0.1. To keep the ripple ages across them add; and that sum is and C4 they are applied across R] to the same levels in a half-wave circuit, applied to the load, RL. that product must be about 0.15. In other In the circuit shown in Fig. 3-b, during Specifying the diode and transformer words, since we must assume the load to positive half-cycles, Cl is charged to the When the rectifying diode is not con- be fixed, the value of the capacitor must peak supply voltage through DI. During ducting, twice the peak supply or trans- be more than 50% higher than for the full - negative half-cycles D2 conducts,, allow- former secondary voltage may be across wave circuit. ing C2 to be charged to the peak supply the device. This is true for all full -wave, We want to mention one more thing voltage. In addition, the previously half-wave and, voltage -multiplier circuits about ripple before we move on. If the charged Cl discharges through D2 to C2. with the exception of the full -wave voltage across the filter capacitor varies The supply voltage and the voltage across bridge. So when designing a power sup- during the cycle, the mean DC voltage Cl are then summed in C2; and that sum, ply circuit, be certain that the diodes have output will be somewhat less than its pos- which is nearly twice the supply voltage, a sufficient voltage rating. sible maximum. Thus, for maximum DC is applied to the load, R1 , when the wave- The average current flowing through output, the ripple must be very low. form goes positive and D2 is once again the diode is equal to the voltage across the cut off. load resistor divided by its resistance. The Full -wave bridge diode once again must be capable of ac- The circuit shown in Fig. 2 shows an- commodating that amount of current. other type of full -wave rectifier, the full - Power dissipation capabilities of the di- wave bridge. Notice that it does not nor- ode are limited. Information as to just mally require the use of transformer, al- 117 what these limits are is supplied by the though one can be used if the input VAC manufacturer and can be found on data voltage needs to be stepped up or down. sheets. The power the diode must be able Let's see how that circuit works. Dur- to dissipate is equal to the average current ing positive halfcycles, current flows it passes in the forward direction multi- through D1, RL, and D4. During the plied by I volt. At times, it may be neces- negative half-cycle current flows through sary to mount the diode on a heat sink so D2, RL and D3. Note that the current that its operating temperature will not ex- always flows in the same direction regard- 117 ceed its specified limit. less of the polarity of the input voltage and VAC When a circuit involving a diode is first that the end of RL marked + is always turned on, the filter capacitor being positive with respect to the end marked charged by the DC behaves as a short

- . As before, a capacitor is usually wired circuit. Because of that, a large initial FIG. 3-TWO VOLTAGE DOUBLERS. These cir- across the load resistor to filter out the current surges through the diode. That cuits are used between the AC source and the ripple. rectifier circuit to nearly double the level of the surge current is equal to the supply -volt- DC output. age peaks divided by all resistance in the Voltage doubler circuit other than the resistances wired When a transformer is used in a rectifier Combinations of these circuits can be across the shorting capacitor. If the surge used to form tripiers, quadruplers, and so current is more than the diodes being used on. A tripler is shown in Fig. 4-a. In it, the can accommodate, the device will be portion of the circuit involving D1, D2, damaged. The best way to avoid damage Cl, and C2 is identical to the circuit is to use diodes that can safely handle that shown in Fig. 3-b,while the D3 -C3 por- initial current surge. Alternately, you can tion behaves just as the D2 -C2 circuit of connect a small resistor in series with Fig. 3-a. The sum of the voltages across each diode to limit current surges to safe C2 and C3 are applied across RL. levels. As for the quadrupler circuit, shown in As for the transformer, it, too, can over- Fig. 4-b, two circuits similar to the one heat if it conducts excessive quantities of FIG. 2-A FULL -WAVE BRIDGE RECTIFIER uses a is oper- four diodes but eliminates the need for a trans- shown in Fig. 3-b, are used. After the two current. To check if transformer former. double voltages are developed across C2 ating within reasonable temperature lim-

76 its, first measure the cold resistance of one that the proper current is available at the winding while noting the ambient tem- base of Ql to keep it turned on and out of perature in °C. Refer to that as Rc, the saturation at all times. cold resistance. Then apply power to the Several improvements can be made in UNREGULATED transformer while its output is loaded as it DC the circuit shown in Fig. 5-a. Those are would be normally. Be sure that all en- shown in Fig. 6. vironmental factors (ambient tempera- In order to achieve good regulation, the ture, etc.) are what they would be under Zener diode should see a high impedance. normal operating conditions and run the In Fig. 5-a it sees an impedance equal to transformer for eight hours. After that RL multiplied by the beta of Q1. To in- time, remove the power from the circuit. crease the impedance, a Darlington cir- Immediately after removing the power, cuit can be used rather than an individual check the hot resistance, RH, of the wind- pass transistor. Such a Darlington pair is ing. Be sure that nothing is connected UNREGULATED shown in Fig. 6 as QI and Q2. The imped- across this winding. The temperature rise DC ance seen by Dl in that circuit is essen- of the transformer, in °C is: tially the product of the betas of the two transistors multiplied by RL. AT = 254 To further improve regulation, a con- RcRc/ stant current should be applied to D1 and Add the value you get for AT to Rc. If the FIG. 5-SERIES REGULATOR CIRCUITS. The to the base -emitter circuits of the series total exceeds 90°C you should start to be one in a provides a fixed voltage while the out- transistors. The circuit around Q3 estab- put from the one in b can be varied using R2. concerned. If it exceeds 105°C, then the lishes that constant current. Current flows transformer is overheating and a different through D3, D4, and R1 due to the voltage transformer should be used in the circuit. D1 which causes a fixed voltage to be from the unregulated DC supply. The volt- developed across D1. In Fig. 5-a, current age across the two forward -biased diodes, Regulated power supplies flowing through R1 also flows through the D3 and D4, is relatively fixed at 1.4 volts Throughout the discussion, it was as- base -emitter junction of Ql. A fixed volt- (0.7 volt across each diode). That voltage sumed that the line voltage is fixed at 117 - age, about 0.6 or 0.7 volt, is developed is between the upper end of R2 and the volts AC and that the load does not change across this junction, turning on Q1. The base of Q3. Because the base -emitter in resistance but remains a constant RL. If voltage between the emitter of Q1 and junction of Q3 is turned on at 0.7 volt, the anyone assumes that to be a realistic con- ground, or across RL, is about 0.7 volt balance of the 1.4 volt, or 0.7 volt, is dition, then he is living in a dream world. plus the voltage across Dl. That fixed across R2. The fixed emitter current, in Line voltage fluctuates from minute to voltage is across RL regardless of supply - milliamps, is 0.71R2. The collector cur- minute. Over time it can vary ± 10% or voltage or load variations. rent is just about equal to the emitter cur- more. During periods of extremely heavy In that circuit, little current flows rent of Q3 and the collector and emitter usage, power companies have been through the Zener diode. What does flow currents do not fluctuate to any degree. known to greatly reduce voltage levels. is limited to safe values by R1. The current The collector current is applied to the As for the load, it is seldom a fixed that is supplied to RL flows through Ql. If Zener diode and base of Q2. Resistor R2 resistor. If the supply is feeding an audio, the required load current is high, Q1 is selected to set the current at the desired RF, or electronic -switching circuit, the should be rated adequately and mounted level. load impedance varies, sometimes from on a heat sink. Circuit components must In the event that a short is placed acci- instant -to -instant, with the signal or be chosen so that the transistor is not in dentally across RL, excess current will switch current fed to it. saturation at any time. flow through Q1, which is likely to de- A fixed, stable voltage is frequently The regulated output -voltage can be stroy the device. The circuit around Q4 required when powering an electronic cir- varied by simply placing a potentiometer performs the function of protecting Q1 in cuit. That constant voltage is not present across the Zener diode and connecting its the event of a short. when there are either supply -voltage or wiper, rather than the cathode of Dl, to Transistor Q4 is turned off when the load variations. As we discussed earlier in the base of Ql. That is shown in Fig. 5-b. current flow through the circuit is at its this series, a fixed voltage developed Now, the voltage across RL is the sum of normal level. It remains off until the cur- across a Zener diode can be used to stabil- the voltages between the wiper of the po- rent flowing through R4, which is also the ize the voltage across a load if the Zener is tentiometer and ground, which is the volt- current through the load, is sufficient to placed across that component or circuit. age between the base and emitter of the develop about 1.4 volts across the resistor. That is fine where low currents are in- transistor. Resistor R1 must be selected so Notice in Fig. 6 that Q4's collector is volved. But when large quantities of current must flow through the load, the Zener diode can seldom be used economically as the sole regulating device for the circuit. Series, parallel, and feedback cir- 1 R2 D3 @Ot cuits using Zener diodes along with one or more transistors have been developed o 04 as practical regulators. UNREGULATED CR)Q4 D2 DC Series regulators

In the series -regulator circuit, DC cur- !R1 ¡Di ;R3 RL rent flows from the unregulated portion of the DC power supply through a transistor to the load. If the circuits are like the ones shown in Fig. 5, the voltage across the load is regulated. In both of those circuits, FIG. 6-THE BASIC SERIES regulator circuit can be improved by using a Darlington pair in place of 01 current flows through RI and Zener diode and adding a constant -current source.

77 connected to the junction of Q2, Q3, and inverting input of the op -amp. The output Q1. The D1. When Q4 is on, it draws the bulk of from the op -amp is passed on to the current from Q3 so that insufficient voltage at the emitter of Ql, which is close of the op -amp, current remains to fully turn on the base - UNREGULATED to the voltage at the output emitter junctions of Q1 and Q2. That also DC is fed back through RF to the inverting reduces Ql's collector current. Thus, less input terminal of the op amp. That invert- it ing input is connected to ground through power is dissipated by Q1, preventing a from being destroyed due to the presence RIN. The voltage at the inverting input, to the of an excessively heavy load. and at the emitter of Q1, is equal voltage at the non -inverting input multi- Parallel regulators plied by 1 + (RF/RIN). The output voltage is therefore fixed by the voltage across D1, There are two types of parallel regulator o the setting of R2, and the ratio of resistors circuits-one supplying a voltage that is UNREGULATED input. only slightly lower than the breakdown DC RE and RIN at the inverting voltage of the Zener diode used in the In Fig. 8 we've added a circuit to pro- circuit, and one supplying a voltage that is tect against damage in the event there is a the di- demand for excessive current from the considerably higher than that of b ode. Both are shown in Fig. 7. regulator. Excess current flow can not destroy In Fig. 7-a, current flows through R1, FIG. 7-PARALLEL REGULATOR CIRCUITS. only damage a transistor, but can the Zener Tran- D1, and the base -emitter junction of Ql. The output from a is 0.7 voit above an op -amp, and consequently an IC. the output from b is consid- across D1 breakdown voltage; sistor Q2 is in the IC to protect it from Fixed voltages are developed erably higher. and the base -emitter junction of Ql. The being damaged. When excess current sum of those two voltages is the regulated flows, sufficient voltage is developed voltage applied across RL. across R3 to turn on Q2. When turned on, is across In Fig. 7-b, current flows through Rl, the base -collector circuit of Q2 R2. the base -emitter junction of transistor the base -emitter circuit of Ql, preventing Q1, and Zener diode D1. A fixed voltage it from conducting excess current. is developed between the emitter and col- Crowbar circuits lector of Ql. The circuit's regulated out- RL put, VR, which is across RL, is equal to UNREGULATED A crowbar circuit is used to prevent Dc in the the sum of the Zener voltage, VZ, and the . damage to a regulated power supply : R3 voltage developed across Ql. It can be event a high voltage is applied across the Q3 Fig. shown that that voltage is equal to: load. In the arrangement shown in 10, the inverting input of the op -amp is /R2+Rg 01 V2 fixed at the breakdown voltage of D1. Re- R3 f1\ / sistors R2 and R3 are selected so that with RL, the voltage at Resistor R4 is critical in and must be FIG. 8-THIS REGULATOR circuit uses feed- normal voltage across selected by trial and error. That resistor back. the non -inverting input of the òp -amp is should be selected for the minimum variation of voltage across RL as the unregu- I- lated input voltage is varied from its minimum to its maximum. by using R1 Performance can be improved QI Darlington pairs rather than individual 83 Rl with a 'OA transistors and by replacing UNREGULATED constant -current source. DC R2; RIN Feedback regulators 1 D1 Q2 A commonly used series regulator -circuit using feedback is shown in Fig. 8. 4-- Current from R2 flows into both the __ box is collector of Q3 and the base of Q2. Be- FIG. 9-REGULATOR CIRCUITS are commonly found in IC form. The circuitry within the dashed in the IC. cause of D1, the emitter of Q3 is at a fixed usually contained voltage with respect to ground. Note that input the regulated voltage is across RL as well rent than before remains for RL. less than the voltage at the inverting op -amp is nega- as across R3 so that R3 can be used to In the opposite condition, when the and the output from the nega- adjust the voltage across RL. voltage across R3 and RL is below the tive. The gate of SCR1 is then also the Should voltage VR across RL increase desired fixed level, less current flows tive with respect to its cathode so that above the desired level, the voltage at the through Q3. More current is now avail- SCR remains off. across base of Q3 rises. That transistor conducts able to flow through Q2 and Q1, rebuild- When a high voltage is applied inver- more heavily than when VR was at its ing the output voltage to its desired level. RL, the voltage across DI and at the proper level. The base of Q3 is then more ting input of the op -amp, remain fixed. positive with respect to its emitter than it IC regulators But the voltage at the non -inverting input R3 was when the level of VR was correct. Figure 9 shows a typical IC regulator increases. Divider resistors R2 and voltage at That causes the transistor to draw more and some of its surrounding circuitry; the should be selected so that the that at the current than it did before from R2, reduc- part of the circuit enclosed by the dashed the non -inverting input exceeds ing the amount of current previously box is usually part of the IC. inverting input when a high voltage from available for the base of Q2. Because cur- A fixed voltage is developed across Dl. an external source is applied across RL. rent through Q2, and consequently the A portion of that voltage, as set by R2, is When such a high voltage is across RL the current through Q1, are reduced, less cur - applied as a reference voltage to the non - continued on page 134

78 LJ HOME CONTROL COMPUTER If you've ever wanted to use your computer to control external appliances or systems-but didn't want to tie up your computer solely for that purpose-then this controller is for you!

STEVEN E. SARNS

HOW OFTEN HAVE YOU THOUGHT: "IF ONLY I COULD Security systems: A "smart" security system could hook my computer up to that furnace (or model train, arm itself in your absence. And the alarm could be coffee pot, security system, etc.), then I could really get dependent on the type or source of breach. For example, it to do what I want"? You probably gave up the idea for with external circuitry, the system could be interfaced to one óf two reasons. First, your computer is too expen- the telephone to alert the police if it sensed a break-in, sive to be relegated to turning on a coffee pot 15 minutes or it could phone the fire department if it sensed a fire. before you wake up (especially when you can buy Robotics: Even the most drole robot requires some inexpensive timers to do the same thing). Second, amount of "smarts." Now you can afford-both in your computer is not designed for such control dollars and in development time-to give him tasks and requires some modifications. some real power. Imagine the con- Those are good reasons to abandon the venience of independent drive- and idea. But what if you had an inexpen- sensory -systems. Imagine how sive computer that could be pro- much faster your develop- grammed easily and had an I/O ment would be with a structure designed specifi- complete computer cally for control ap- system for each func- plications? Then you tion. could put some of Model control: your ideas into ac- Imagine the complex- tion. This control ity that you could computer that you build into a computer- can build has- controlled model - along with its many train layout, or the acro- other I/O cababilities- batic maneuvers that could the ability to control BSR be programmed into your radio - type wireless remote -control controlled model airplane. modules. And the computer can be Home entertainment: A computer- programmed in BASIC using any ter- controlled servo tracking system can posi- minal (or a computer configured as a ter- tion your antenna on the satellite of your minal) that has an RS -232 serial port. choice. Let's take' a quick look at the abundance of Home energy management: (This is what the au- applications for a control computer that surround thor's prototype was designed for.) The living-room you-some of which you've probably considered and, thermostat could be the first target-it could automat- perhaps, some you've never even thought of. We won't ically set back when you are at work and warm up before go into detail on how to use the controller for the you return (but not on weekends). If you have electric following applications. Keep in mind that your pro- heat, and if your electric company has peak and off- gramming capabilities may limit what you want to do. peak rates, your electric bills could be cut in half by (You need to know at least BASIC programming to use averaging your power requirements instead of turning the controller.) But we will explain how to use the everything on at once. Remember-any equipment you control computer in enough detail so that you'll be able purchase for energy management or control might be a to tailor it to your own applications. tax credit for you. You'll have to check your own state's

79 A15-A8, pins 39, 2-8), laws. If you're lucky, you might effec- personal computer. (Anyone who owns an dress lines, (IC18 tively cut the cost of your project in half! IBM PC has a complete set of develop- and 8 low -order address lines coming ment tools for this board.) The 8088 can from the latch outputs, A7-A0, (IC15 pins Features of the controller be thought of as being made up of two 7, 12, 6, 15, 5, 16, 2, 19). We also have 8 from The underlying design goal for this units:The first is the BIU or Bus interface bi-directional data lines, AD7-ADO (IC18 pins controller was a small, inexpensive, yet Unit, which prefetches instructions while the input side of the latch still contain powerful control computer with its own the rest of microprocessor (the EU-Ex- 9-16). Note that the data lines development system. That design had to ecution Unit) is working on the current the multiplexed address -information. at the time the achieve a successful balance: We wanted instruction. Besides speeding execution, They will contain data RR) is ac- the board size and the cost to be kept that has an even more fortunate (econom- appropriate control line (RD or down, yet we still wanted to include as ical) effect: Memory IC's with access tive. divided into many features as we could. However, if times as slow as 400 ns will work on the The memory field must be IC's). We we tried to give the board too many bells board. appropriate banks (or peripheral and whistles, the resulting high cost must make sure that only a single pe- one time. would limit its practical (economical) ap- The bus structure ripheral IC can be active at any plications. On the other hand, a cost -con- The microprocessor is connected to the If more than one device attempts to place simul- servative approach would result in a board memory and I/O through the data bus, the data on the bi-directional data bus with only limited applications. Of course, address bus and the control bus. Those taneously. a condition known as bus con- contention we searched for a happy medium. busses are shown in the computer's sche- tention rises. The result of bus and, con- The result was a rather small board matic in Fig. 1. is an undefined bus state lines sequently, undefined operation. Thus the (about 51/2 x 61/2 inches) that has enough The data bus is the group of eight will be a power to do its job at a competitive cost- (Do-D7) over which data can be transferred output of our memory decoder one output will be take a look at the controller's features: between the microprocessor and any one -of-N type-only out- total of 46 inputs and outputs: memory or I/O (input/Output) device. active at any one time. Each of those A chip -enable Seven high -current, individually ad- The address bus is made up of. 20 lines, puts will be connected to the a IC. dressable outputs; 7 individually ad- some of which are time multiplexed. (rE) input of peripheral of the size and type of dressable inputs; 2 eight -bit input ports, Don't worry about that now-we'll get to The selection is heavily influenced by our need 2 eight -bit output ports. it shortly. You should know, however, that memory and program into An RS -232 serial port: a terminal can the microprocessor uses the address bus to to convert our finished simply remove a RAM IC be used for program entry. select the desired memory address or I/O ROM. If we can it with a pin -compatible An eight -channel, 8 -bit analog -to- device to send data to or receive data and replace a compact yet flexible digital converter with provisions for digi- from. That address is represented by the ROM, we will have 2016 2K x 8 RAM and the tal -to -analog conversion. unique combination of address -line board. The -compatible, choice of two operating systems: states. 2716 2K x 8 EPROM are pin A also need memo- BASIC or Forth. The high-level language We will be concerned with three lines so they will be used. We -ed development tools will cut your programming time by 90%. of the control bus. The READ (RD) and ry space for ROM the that can be used during the program test- An on -board EPROM programmer WRITE (RR) lines determine whether by) or ing. and an empty socket for the blank makes a permanent copy of your RAM - data is to be transferred to (read be programmed. based program. from (written by) the microprocessor on EPROM to real-time clock for time -of-day the bi-directional data lines. The third Throughout the remaining description A address functions. line, ior, is used to distinguish between of the board, the highest order The ad- Auto start of ROM -based programs. a memory access or an I/O access. lines (A19 -Ale) will be ignored. A15-A8 will be called the high - BSR-type remote controller is on a The 8088 can address 1 megabyte (220) dress lines significant companion power -supply board. That of memory with its 20 address lines. If we order address lines. The most can be used system communicates to readily available use only the lower 16 lines, we can ad- high order address line (Au) Address receiver modules that you simply plug dress 64K. The 8088 combines the data to chip -select the system ROM. the inputs to a into the AC lines. All of the hassles of bus and the lower eight address lines into lines All and Al2 are used as which stringing wires from the controller to the what is called a time -multiplexed bus. 74LS139 one -of-4 decoder (IC16), other mem- control point are eliminated. That was done so that the 8088's package will be used to chip -select the could be kept to 40 pins. The first design ory IC's. We have mapped our system A closer look question is to decide whether to de - ROM and 4 memory sockets uniquely Table 1 shows Now that we have an idea of the basic multiplex the data and address bus or use into the 64K address space. let's discuss it as is. Intel (and others) supports the features of the controller, TABLE 1-MEMORY MAP some of the theory behind it. Unfor- multiplexed bus with an extensive range the bus multiplexed tunately, we won't be able to cover all of of products. Leaving Address (hex) IC/Function to the points that we just mentioned this will result in a smaller board that is easy 0000-07FF 1C12/RAM month-they will be discussed in upcom- lay out. (That is one of our design goals.) 0800-OFFF IC10/RAM ing installments of this article. However, because of the popularity of the 1000-17FF IC13/ROM We'll start by describing the micro- non -multiplexed bus, peripheral IC's de- 1800-1FFF IC14/ROM and processor and the support circuitry re- signed for it are more available and are EPROM programming to test, debug and program the less expensive. Because another of our quired socket be dis- design goals is to design a low-cost board, basic system. The design will IC9/System we must stick to popular components-or 8000-FFFF cussed in enough detail so that even those ROM who are not familiar with microprocessor at least ones that we expect to become Note that design techniques will be able to get an popular. Fortunately, demultiplexing the a memory map of our system. A15 IC19 to select the system overview of the process. The control combus is an easy matter; it requires only a set is inverted by -of-4 decoder puter's schematic is shown in Fig. 1. of latches. A 74LS373 octal latch (IC15) ROM and that the one The microprocessor selected for this is used. It is enabled by the ALE (Address (IC16) is qualified by IC17-d: when A15 project is the Intel 8088-the 16 -bit mi- Latch Enable) pin of the microprocessor and the to/M lines are low, a memory-field croprocessor that forms the heart of IBM's (pin 25). Now we have 8 high -order ad- operation is indicated.

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FIG. 2 --THE FOIL PATTERN FOR the control computer's component side is shown above.

When the 8088 is reset, it will begin taken directly from stabilized address and OR gate is applied to the 2716 óE pin (pin execution at address FFFFßH. That data busses. The disadvantage of our ap- 20). means our system ROM should occupy proach is that the microprocessor cannot The 2716's ce/PGM line (pin 18) will be the highest memory position. (Remember be doing anything else during that 50 -ms normally low and go high whenever cm that we're not decoding the highest -order interval when the busses are stabilized- and wR are true. Those two signals (at address lines, so that when the 8088 looks including timing the 50 milliseconds. We IC20, pins 1 and 2) are the trigger condi- at address FFFFO, it will see the system will have to use a hardware timer. The tions for the 74LS 123 50 -ms one shot ROM. advantages of our method are fewer com- whose output (IC20, pin 4) is connected ponents, software simplicity, and a small to the 8088 RDY input and the 2716 Cg/ EPROM programming board size. (Figures 2 and 3 show full- PGM input. Whenever the RDY line is low, Programming the 2716 EPROM is a sized foil patterns for the double -sided the 8088 inserts wait states into the cur- simple matter. The programming voltage printed -circuit computer board. The rent microprocessor instruction. The wait may be applied as a DC voltage to pin 21, power supply for the computer is con- state holds the current bus status (for 50 the v,1. pin. The address and data must be tained on a second board. We'll talk about ms, as determined by C14 and RIO) until stabilized for 50 milliseconds, and during that board in a future installment of this the ROY line is returned high. that time, a single TTL-level pulse is ap- article.) In fact, the EPROM programmer The specifications for the programming plied to the ce/PGM pin (pin 18). (It is is completely invisible to the software- voltage are + 25 ± .5 volts DC at 30 mil- pulsed from low to high.) the EPROM appears to the operator as a liamps. We have found that reliable pro- Rather than the more usual method of very slow -to -write RAM -like device. gramming can be achieved with a surrounding the EPROM being pro- We will operate the 2716 from the mi- programming voltage as low as 22 volts. grammed with a bi-directional latch, the croprocessor bus by externally qualifying (A programming voltage of 24 volts has address and data information will be tzo and cs with IC17-a. The output of that worked well for us.) The maximum Vpp

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FIG. 3-THE SOLDER SIDE of the computer printed -circuit beard.

voltage specification is an extremely im- only setting appropriate locations to "0." light is much more intense than it appears portant one to follow. We met up with A fully erased EPROM has all of its mem- and quickly damages the eyes. Place the disaster with a programming voltage of 26 ory locations filled with l's. EPROMS to be erased within one inch of volts. If the VPv voltage is exceeded even The time will come-either because of the bulb and leave it on for 10-15 minutes. for a few nanoseconds, the EPROM will a programming mistake or because you no That should change all the bits in the fry! That means that the V supply must longer need a particular program-that EPROM to l's. not Overshoot during turn-on or turn-off. you'll want to erase your programmed The microprocessor requires a system Because we need to control the ramp -on EPROM. You can erase the EPROM's by clock signal, which we obtain with a con- and -off characteristics we will use a exposing them to ultraviolet light. Direct ventional TTL-type crystal oscillator power supply design that always switches sunlight will erase an EPROM in about a (IC 19, XTAL I, and other associated com- the supply on and off for each byte pro- week. Room -level fluorescent light will ponents). The frequency of the clock is grammed. (The switching supply makes erase an EPROM in about 3 years. (Al- 4.00 MHz, even though the 8088 could the control computer more versatile be- though that's not an efficient erasure run at 5 MHz. The 33% duty -cycle con- cause it allows you to use other method, it is still a good idea to cover the straint on the clock signal would require EPROM's-for example the 2732-that window with a label to block out room/ either a special clock generator or addi- require a switched V supply. The 2716 sun light.) A commercial EPROM eraser tional TTL chips. doesn't require a switched supply.) That is simply a source of ultraviolet (UV) light A reset pulse is also required by the switching programming supply is located that irradiates the EPROM. You can make 8088, which we generate by using one- on the separate power supply board. We'll one yourself with a General Electric half of a 74LS123 (IC20-a) during power- discuss that circuit and its construction in G15TB 18 -inch germicidal bulb in a con- up or whenever the reset line is grounded a future part of this article. ventional fluorescent -lamp holder. Do and released. Programming an EPROM involves not look into the bulb when it is on. The continued overleaf

83 The I/O The RS -232 port can be implemented holding register until the microprocessor The RS -232 port is really part of the I/O in two distinctly different manners. The requires it. Transmission is simply a mat- system, which we'll be discussing in a first and easiest is to use a UART (Univer- ter of writing the character to the UART's future installment of this article. However, sal Asynchronous Receiver Transmitter) transmit register. we must introduce it now because it is IC. The UART constantly waits for an The other alternative-the one that required for any operator 1/O. It also must incoming character, receives it according we'll use-is to use one input and one be used to confirm proper operation of the to whatever protocol has been pro- output of the board to send and receive the basic system. grammed, and stores the character in a serial data. That method requires the microprocessor to assume control of the entire process of data reception and PARTS LIST- COMPUTER BOARD transmission. However, it eliminates the requirement for a large and expensive All resistors 1/4 -watt, 5% unless other- 1C14-EPROM to be programmed component. The principal limitation of wise noted IC11-74LS259 8 -bit addressable latch this approach is that the microprocessor R1,R4,R14-R18-1000 ohms IC15-74LS373 octal latch must when to R2,R5,R6-user-determined. To be dis- IC16-74LS139 dual 2 -to -4 line decoder/ know expect a character and cussed next month multiplexer it must be executing its input routine be- R3,R11,R12-10,000 ohms IC17-74LS32 quad OR gate fore the character is sent to the board. R7-680 ohms IC18-8088 microprocessor That's not a problem for most applica- R8-390 ohms IC19-74LSO4 hex inverter tions. In the case of BASIC, it means that R9-12,000 ohms IC20-74LS123 dual one-shot all console commands and program IN- R10-2,000 ohms Q1,Q2-2N3904 PUT statements are handled easily. R13-10 ohms Q3 -2N3906 However, there can be no INKEY$ state- RN1-4.7K x 9 resistor network D1,D2, D4-D8-1N4148 ment. Capacitors D3 -1N4001 Cl-user-determined. Miscellaneous: IC sockets, PC board, The eighth output and eighth input of C2-150 pF, ceramic disc mounting hardware, etc. the bit -addressable I/O port will be used C3-C8,C11-C13,C16-C20-0.1 µF, ce- The following are available from Vesta to implement the RS -232 port. The re- ramic disc Technology, Inc., 2849 W. 35th Ave., quirement for a negative voltage supply CO 0.001 µF Denver, CO 80211: KIT 1-Kit of all parts for the RS -232 link can be avoided with a C10-27 pF needed to control 7 LS-TTL outputs, bit of foxy circuit design. The incoming Cl 4,C15 -10µF, 16 volts, electrolytic monitor 7 inputs, program EPROM's, RS -232 signal is normally at the "mark" Semiconductors RS -232 serial port, and 2K RAM (does or negative level. Every character trans- IC1-ADC0804 A/D converter (National) not include operating system-see be- mission ends with a stop bit designed to IC2,IC3-74LS541 octal buffer and line low), $99.95; KIT 2-Kit of all parts for driver full -capacity I/O and 4K RAM (does not return the line to the negative level. We IC4-SN75478 seven high -current include operating system-see be- can generate our level from the incoming darlington drivers (TI, also Sprague low), 169.95; Operating systems con- RS -232 line. That approach works fine for ULN-2003, Motorola MC1413) tained in ROM: BASIC I operating cables of less than 10 feet long. If longer IC5-4051 8 -input analog multiplexer system, $12.95; BASIC II operating cables are used, a separate negative sup- IC6,IC7-74LS377 octal latch system, $29.95; Forth operating sys- ply between -5 and -12 volts DC 1C8-74LS251 8 -input digital multiplexer tem, $79.95; Assembled, tested, and should be used. Such a supply is available IC9-System ROM. 2716, 2732, or 2764. burned -in control computer with from the power -supply board, which-as 450 ns maximum access time. BASIC Il operating system, $279; we mentioned we'll IC10,1C12-TMM 2016P-2 (Toshiba or RS -232 cable, $24.95; 2716 EPROM, previously- discuss in a similar) 2K x 8 static RAM, 450 ns. $6.95. Add $6 for shipping, handling, future installment. IC13-Programmed EPROM (2716) and insurance. When examining serial asynchronous waveforms, remember that a logic one is PARTS LIST-POWER -SUPPLY/ less than -3 volts DC and a logic zero is BSR LINK BOARD greater than + 3 volts DC. The line is held All resistors 1/4 watt, 5% unless other- (Sprague) in the mark or one state when not active. wise noted IC2-TL497 switching regulator The transmission always begins with a R1,R19-200 ohms IC3-74LS00 quad NAND gate start bit = o and ends with a stop bit = 1. R2,R7,R8,R20-100 ohms IC4-LM340-5 + 5 -volt regulator The stop bit returns the line to the mark R3,R4,R11,R12,R15-1000 ohms IC5-LM320-5 -5 -volt regulator R6,R10-4700 ohms Q1 -2N3904 state. R9-1 ohm (a jumper works fine) Q2 -2N3906 Full duplex serial operation that means R13-10,000 ohms trimmer potentiome- D1,D3,D5,D6,D10-1 N4001 separate wires carry data to and from the ter D2, D4, D7-D9-1 N4148 control computer (and terminal). Pin 2 of R14-15,000 ohms T1 -11Z2100 1:1:1 pulse transformer the RS -232 connector is transmitted data R16-270 ohms (Sprague) to the computer. Pin 3 is received data R17-10,000 ohms T2-16 volts, center tapped, 0.4 amps. from the computer. At the terminal, those R18-470 ohms (Signal ST-4-16 or similar) two pins are reversed so that pin 2 is an Capacitors S1-normally open momentary pushbut- C1,C2-10 µF, 16 volts, electrolytic ton switch output and pin 3 an input. If you are using C3,C5-0.01 µF, ceramic disc Miscellaneous:line cord, printed -circuit a personal computer as a terminal, you C4,C6-0.047 µF, ceramic disc board, IC sockets, heat sink for regulator, must determine if the RS -232 port of your C7-10 µF, 35 volts, tantalum mounting hardware, etc. computer is configured as a terminal or as C8-.001 µF, ceramic disc a computer. Whatever the case may be, C90.1-- µF, ceramic disc The following are available from Vesta connect the board's input to the terminal's C10-0.14 to 0.47 µF, 150 volts, elec- Technology, Inc., 2849 W. 35th Ave., output and vice versa. trolytic Denver, CO 80211: Power-supply/BSR- C11-3300 µF, 16 volts, electrolytic link kit, including all components, Building the control computer C12-500 µF, 50 volts, electrolytic $59.95; Assembled, tested, and The actual assembly of the controller Semiconductors burned in power supply, $109. Add $6 requires no special techniques for the IC1-ULN2003 darlington array for shipping, handling and insurance. builder. You can use a printed -circuit board (we showed the foil patterns for the 84 -R9-- --{/r23 check adjacent pins and lines for whisker R10 -R11- C14 C18 shorts. Check every IC to insure that no C12 + C15+ -R12- IC18 pin has been folded under during inser-

1 R1 IC19 IC20 S05 tion. Use an ohmmeter to orien- R4 check the tation of every diode. It is unfortunately - RN7 C13 not uncommon to find the markings re- DICCO2I C9 IC15 R8 XTAL1 1 1C16 IC17 versed. If C3 R7 those basic troubleshooting 1 steps don't work, reapply + 5 volts DC C7 C10 D4'}--- -R13- and check the state of the pins on the R2 - C18 microprocessor according to Table 2. IC12 IC13 C10 Reset the board and observe the RS -232 output pin. If there is any activity C8 IC14 on this pin shortly after reset, then the c4 I I _J prompt is being sent, but the terminal is JI 1C9 IC10 r not responding correctly. Check the com- - -i 111603 C171í munications settings on the terminal. (Al-

F ' IJ R51 IC20 though we said that the terminal should be R14 R6 C11 OF j L _i_ JrP1 set to 4800 baud, that's not essential. Sim- C61 i IC5 IC6 IC7 ply type a space within 8 seconds after C11 R15i L reset, and the computer will adapt.) Ex- iT R3 amine the input of the RS -232 port; this S01 SO2 S03 SO4 06 line should be at a TTL low level. Typing C2 C51 R B any character on the terminal should pro- } IC1 IC2 IC3 1C4 117 duce a short series of positive -going D5 pulses. When you get the BASIC prompt, and FIG. 4-PARTS-PLACEMENT DIAGRAM for the computer board. The dashed lines represent foil -side your terminal and the control computer jumpers. There are many "unused" pads; they are for future expansion and experimentation. For are communicating properly, you are example, note that a 28 -pin socket is provided for the 24 -pin 2716 (IC14). That allows larger EPROM's to ready to enter your first program: be programmed. Simply plug the 2716 (or other 24 -pin device) into the socket leaving pins 1 and 2 of the socket unoccupied. OK >NEW double -sided board in Figs. 2 and 3) or board for the power supply and BSR-type OK you can wire -wrap the project. You are controller, you cán test the computer >1 PRINT "HELLO", probably better off with the PC board. board if you have a + 5 -volt DC regulated >2 GOTO 1 Troubleshooting will be easier, and as- supply. >RUN sembly will be quicker-about an hour, Regardless of what supply you use, en- assuming you already have the board. (If sure that it is the correct voltage, and be We hope that everything worked as it you are not able to make your own board, sure to orient it correctly. Reversing the should have, and your screen is now full. see the Parts List for a supplier). Wire - power-supply polarity is like reversing an Well now leave our discussion of the wrapping the project will take about 16 IC, only it's more efficient-it will burn computer board and begin our discussion hours. One note on wire -wrapping: Do out all of the IC's. The BASIC operating about the computer's power supply and not give in to the temptation of wire -wrap- system should be inserted into the system wireless remote control. ping directly to the leads of the discrete ROM socket (IC9). The first memory You may think we're getting ahead of components. The integrity of a wire -wrap socket (IC12) should contain a 2016 RAM joint depends on the square corners of the IC. Do not insert additional memory yet. posts. Also, unneeded I/O should be removed. TABLE 2-8088 PIN STATES If you have the printed -circuit board, Get your terminal to the proper protocol simply follow the parts -placement di- (4800 baud, no parity, 8 data bits, full Pin Function State agram in Fig. 4. Be careful not to create duplex, caps lock on) and connect it to the 1,20 GROUND ground solder bridges, and when you are board. Apply + 5 volts DC. If the BASIC 21 RESET low finished, wash the board in flux solvent. prompt (>) appears, we can assume that 23 TEST high That will remove any flux residues left on the basic microprocessor circuits are cor- 31 HOLD low 19 CLOCK 4 MHz the board. Don't forget that we've shown rect. (If you use the BASIC II operating 17 NMI low the foil and parts -placement diagrams for system, then you do not have to set your 40 v +5 VDC only the computer board. The power sup- terminal to 4800 baud. Simply hit the 22 READY high ply and BSR type controller will be lo- space bar within 7 seconds after the board 24 INTA high cated on a separate board of the same size. is turned on or reset.) 33 MN/MX high We'll discuss that single -sided board next If the BASIC prompt does not appear, 18 INTR IOW time, and we'll give you some more hints then we have some troubleshooting to do. on the control computer's construction. IF YOU DO NOT GET THE PROMPT, TURN OFF the power and disconnect the board. If ourselves because we haven't finished dis- Troubleshooting you are using a wire -wrap or other pro- cussing the computer circuitry yet-spe- After you install all the parts, carefully totype system, check every line with an cifically, the I/O system. But some people inspect your board. You should check that ohmmeter. If you use a printed -circuit will not be able to test out the basic system all IC's are in the correct sockets and that board, examine the board closely (with a until they build a power supply. So now they are correctly oriented. Transistors magnifying glass) for solder bridges or we'll discuss the power -supply board. and diodes should also be checked. Then splats, cold solder joints, solder-flux resi- After we've done that, we'll return to the measure the power-supply voltages. Al- due, or "whiskers" of PC material under computer board with a look at its I10 though we have not yet discussed the the solder mask. Use an ohmmeter to capabilities. 85 TO OPTIONAL BACKUP BATTERY

010 0+ 1N4001

R20 * 10052 1n Sob 117VAC D7 D8 09 R19 C12 2N3906 1N4148 1N4148 1N4148 20052 PWRFAIL 05 1F N I YN o 1N4001 1/4 7400 011 16 1K 5V o D6 15 1N4001 o 1C4 0 14 LM340-5 8 C11 R12 ; R6 o Cl 7 3300/16V C i-. 1K 4.7K o 10/16V 1/4 7400 6 COM C12 4 1/4 7400 11 4 120 Hz 6 13 500/50V C2 R10 5 IC3-b 1 D1 4.7K 12 R16 C9 1N4001 R17 2700 0.1 C 10K 1M 10 -5V 1['S- o - 1! - C11 LM3L0-5 10 120 Hz D3 2N3904 1/4 7400 -12V 1N4001 11 o 9 +12V D2 o 1N4148 N 91 R1 R18 20052 47052 T1 -b 13 RESET 1/3 1:1:1 T1 -c R2 000 6b0,153i:1:1 10002 C2 3C6 VVh .047 .047 IC1-e U1.N2003 C3 't C5 .01 .01 IC1-a 7 10 1/7 ULN2003 14 13 16 T1 -a 15 IC1-d ICI -b 1/3 1:1:1 8 1/7 ULN2003 1/7 ULN2003 R8 10052 31 14 4 w. R9* Lt ICt-c R7 100µH 107 1/7 ULN2003 10052 11 12 R4 IC1-1 IC1-g 1K 1/7 ULN2003 1/7ULN2003 5 12 BSRENo

2 PGM

5 VpP

14 13 10 R14SS ._- C7 15K 10/35V 1C2 TL497 R13 213 4 5 6 7 10K

C8 R15 *SEE TEXT .001 T é:K

FIG. 5-POWER-SUPPLY/REMOTE CONTROLLER schematic. Components that are marked with an asterisk are optional. Note that some component values do not agree with the Parts List that appeared earlier. Those have been updated in the Parts List on page 90. TMM 2016P and 2K x 8 EPROM's like The second board requires a 21 -volt supply at 30 mA. We the 2716 before you start making changes. As we mentioned last time, we know mention the requirements for other Presuming that everything is working that the computer board requires a supply EPROM's because, as you may remem- correctly, then you can begin to change

of + 5 volts DC at less than 1 amp. If you ber, the first installment of this article the board configuration. Let's say, for ex- plan to use an RS -232 cable longer than 10 made note of some "unused pads" on the ample, that you want to program a 2732 or feet, then you'll also need a -5 -volt sup- board, some of which are for jumpers to 2764 EPROM. You will have to connect ply to establish the RS -232 "mark" level. select various options (including the op- pin 23 of the socket (remember-we're And if you'll want to program EPROM's, tion to program EPROM's other than the using 28 -pin sockets even though the 2716 you'll need a higher-voltage supply-the 2716). Unfortunately we cannot go into and 2732 have 24 pins) to Al1. And you'll 2716 EPROM requires a 25 -volt DC sup- detail on all the possible options-we'll have to cut the trace that now brings VPt, ply at 30 mA. discuss a basic configuration and leave the there. Pin 20 of the socket should be con- Other EPROM's require other supplies. experimenting up to you. We strongly rec- nected to IC16, pin 7 instead of IC20 pin For example, the 2732 requires a 21 -volt ommend that you have the board working 13. Study the data sheets and pin func- switched supply at 20 mA, while the 2764 correctly using 2K x 8 RAM's like the tions carefully so that you understand

86 why those changes have to be made- accomplished with IC2, a TL397 switch- activated. That allows approxirriätely 30 before you make any changes. ing regulator. Besides giving us the ability milliseconds of warning before the output to program 2732's, there is an additional of the + 5 -volt supply falls below 4.75 A look at the power supply benefit to switching the V supply: We volts. The PWRFAIL signal is fed (through The schematic of the power supply can control its turn -on characteristics. S06 and SO5) to the non-maskable inter- we'll use is shown in Fig. 5. It can supply That's important because most EPROM's rupt (pin 17) of the microprocessor. The all of the Vpp options. (The level of Vpp specify the programming voltage to with- microprocessor will enter a wait state until can be varied by trimmer potentiometer in .5 volt. If the supply goes any higher, its pin (23) goes low, which will R13.) The power-supply board alto the device can be destroyed. Unfor- happen when a 120 -Hz signal is detected. provides some signals that are used-but tunately, many power supplies generate The 120 -Hz signal will be detected, of not required-by the control computer it- an overshoot greater than .5 volt when course, when AC power is restored. self. Those signals include: PWRFAIL they are switched on or off. Even a few That 120 -Hz signal is a positive -going (which tells the computer that the AC nanoseconds of ringing on the line is pulse at AC zero cross. That signal is power has failed) and a 120 -Hz TTL-level enough to cause some EPROM's to important for several reasons. It allows the pulse that is used for time -of-day routines. crowbar the + 5 -volt supply. control computer to be used for time -of - The ± 5 -volt DC power supply is made The power-fail circuit is a simple com- day applications. (A time -of-day routine up of simple linear-IC regulators (IC4 and mon -base, level -detection circuit that has been included in the BASIC interpre- IC5). The V supply must supply only 30 monitors the voltage across the + 5VDC ter. See the Parts List for ordering infor- mA, but it must be switched on and off for regulator. When that voltage falls to less mation.) The second use of the AC zero - the 2732 type EPROM. The switching is than 4 diode drops, the PWRFAIL signal is cross signal is to synchronize the control

6 5/8 INCHES

=1G. 6-FOIL PATTERN for the power supply remote controller. The single -sided board is the same size is the computer board. 87 Zia S1 computer to the AC line. Many types of RESET machinery require switching on or off at AC zero -crossing to minimize the amount of interference generated. More important -R1- JI J for us is that the the remote -control link -R2- J S06 J requires that transmissions be syn- J

chronized to AC zero crossing. We'll dis- I Cl -C2 -L1--- R3 cuss that shortly. Transistor QI is 1C1 -R11- -R7- -R9- R4 -R12- connected in a common -emitter config- -n- -R8- uration, driving IC3. IC2 1C3 - C3 R10 If you're worried about power failures C4_C5 R13 Lui -514- and brownouts, you can make the power C6- -R15- IC7 -Ri6- -R17- J supply uninterruptable by adding an op- C8

D 10, and R20. That 1 3 tional backup battery, 419 D2 approach is simple and effective for small 5 Ti 6 UZ 4 systems such as this, where an 8 -volt, 4 2 C10 I$ID4I RI19 amp -hour Gel -Cell will give you about 6 01 *iiIIT*T*RI18I 1 3 4 hours of backup operation. Unfortunately, 2 03 D6 while a battery -backup system will protect the contents of RAM, it will not pro- D5 tti39* tect the time -keeping function, which C11 relies on the 60 -Hz line frequency. 0 The foil pattern for the single -sided power-supply/remote-control board is R20 DIO shown in Fig. 6. Note that it's the same C12 size as the computer board that we showed to you earlier. The parts -placement di- 8 7 agram for the board is shown in Fig. 7. Building the power supply is simply a matter of "stuffing the board." There are ----i a few points that we should mention, 8 OPTIONAL though. Figure shows the assembled BACKUP board of the author's prototype. Note that BATTERY only one regulator is installed. That's be-

cause the -5 -volt supply is necessary 1 1 7 V A C only for RS -232 cables longer than 10 feet. Up at the top of the board is S06-a FIG. 7 -PARTS -PLACEMENT diagram for power supply/remote controller. standard 16 -pin IC socket. A I6 -conductor cable that leads to the computer board frequency signal onto the AC power lines. that everything is all right. Because of is simply plugged in there. That signal contains information that is that, you should be very careful if yoú The flat PC -mounted transformer and decoded by the receiver module. There plan to use this system in any application the heatsink for the regulators bring the are many advantages to using carrier -cur- that requires high reliability. However, in overall height of the power supply to less rent communications. First, the wires are the home environment where the system than 1.5 inches. That means that even with already there-there is no need to drill, was designed to operate, it is as secure and the computer board mounted directly on cover, or hide the wires around the home. reliable as possible for the low module top of the power supply, the total height Second, the system is highly portable- cost. can be kept well below three inches. because there are no wires, it is not built There are several possible problems into your existing location. Another ad- with transmitting information over the AC The remote -control link vantage is that the system is popular- power lines. First, if you live in an apart- The greatest feature of the power -sup- Radio Shack, Heath, Sears Roebuck, and ment complex, you may find that your ply board is the wireless remote -control Advance Electronics are among the transmissions control your neighbor's link that allows the computer to control largest suppliers. The receiver modules units as well as your own. But because instruments and appliances without the are inexpensive ($8-$17) and are avail- there are 256 unit codes available, a bit of hassles of stringing wires to the control able for a wide variety of functions. Plug- coordination will easily solve that prob- point. Signals are sent via the power lines in modules (see Fig. 9), wall -mounted lem. The second problem occurs when and are decoded at the control site so that switches, and dual outlets are the most attempting to transmit from one branch of remote control is simply a matter of plug- common. the AC line to the other. When 230 volts ging the unit that you want to control into There are two basic types of receivers. AC is brought into the home at the service a remote module, and transmitting the The lamp controller uses a Triac as the entrance, the home circuits are shared be- appropriate codes to the module under control element and can regulate the AC tween the two phases. A transmitter on control of a BASIC program. (We're get- power into resistive loads up to 300 watts. one leg may not be able to communicate ting a little ahead of ourselves here; we The appliance modules contain a relay with a receiver on the other. Many times, haven't yet discussed the computer's I/O that can be used to switch loads that draw however, appliances that are connected system that enables us to do that. But up to 15 amps. between the 230 -volt phases will serve as we'll get to the details on that shortly.) It should be noted that this system does a high -frequency bypass path between the The best way to familiarize you with the not include "handshaking." No response legs. If a problem is encountered, a 0.11.1F remote -control system is to compare it to from the receiver is expected; it cannot capacitor connected across the legs the BSR model X -10-a remote -control indicate that the message was received or should solve it. (The capacitor provides a system based on the carrier-current meth- that the command was executed. The high -frequency bypass path around the od. A transmitter superimposes a high - transmitter simply transmits and assumes transformer to the other leg.)

88 complements) data packet consists of 4 bits that determine the "house code" (A- ,+r ,.z_.... P) followed by 5 bits that contain either . 4/ 3 1 i, . f.«{ ««.....«.te.:e5..,..«. the command or unit code. A typical con- .«. trol -command sequence consists of two .tt«..r..,-. 16 -CONDUCTOR transmissions. First, for example, house RIBBON CABLE code M, unit 3 is transmitted. That causes TO COMPUTER BOARD all modules that are set to code M-except for any modules set to unit 3-to ignore the next transmission. (Of course, any modules that HINGED HEAT are not set to house -code SPACER SINK M will also ignore the next transmission.) That next transmission would be, for example, house -code M, ON. And module 3-which is the only module "paying attention" responds by turning on. Table 3 lists the house codes and Table 4 lists the command codes that are available in the system. Notice that if you select house code M, the upper 4 bits are always zero. The data word transmitted then consists of only the following 5 -bit word-the decimal value shown in Table 4. If you wish to use other house codes, simply form the 9 -bit word by placing the house code bits in front of the command bits. We'll look at an example shortly. The hardware required to transmit the commands is surprisingly simple. The AC zero -cross detector is already a part of our system. The 120 -kHz transmitter is an inductive multivibrator that can be en- GABLE TO LINE abled with a TTL signal (BSREN from pin COR: BaCK.UP BATTERY 11 of SO5). This multivibrator consists of 4 open -collector inverters (ICI) con- FIG. 8-THE ASSEMBLED board. Note that IC5 was not installed in the author's prototype. nected in an astable configuration. Each stage is formed by paralleling two gates for increased reliability. A fifth IC inverter We mentioned that the remote -control over which is superimposed first a one and is connected in a negative -feedback con- system requires that the code transmis- then a zero. Notice that each bit of data is figuration, biased at the same level as the sion be synchronized to AC zero cross- sent during one-half AC cycle. Therefore, multivibrator stages to provide a stable ing-the transmission must begin within the data -transmission rate is 120 Hz. bias source. The multivibrator is control- 100 microseconds of zero cross. A data Each message sent to the control mod- led through two additional (open -collec- "one" bit is defined as 3 bursts of 120 kHz ule is made up of 22 bits of data as shown tor) gates connected to the inputs of the starting immediately after zero cross, last- in Fig. H. That data is organized as fol- astable gates. Those will clamp the asta- ing 1.0 milliseconds, and spaced 1.6 ms lows: First a start sequence of 1,1,1,0 is ble inputs to ground in order to disable the apart. A data "zero" bit is defined as no transmitted. (That takes two full cycles.) oscillator. transmission of 120 kHz after zero cross. Next the 9 -bit address/command code is The software required to drive the BSR Fig. 10 shows one cycle of 117 -volts AC, transmitted. Following each transmitted remote -control link is, unfortunately, not data bit, the compliment of that bit is as simple as the hardware. Because of the transmitted on the next AC zero cross. The complete message, including the start sequence, takes 11 full AC cycles. The 9 -bit (18 bits if you include the TABLE 3

House Code D8 D7 D6 D5 A 0 1 1 0 1.Rms 1.6ms B 1 1 1 0

C 0 0 1 0 D 1 0 1 0 E 0 0 0 1

F 1 0 0 1

G 0 1 0 1

H 1 1 0 1

0 1 1 1 1ms 1ms tms J 1 1 1 1 DATA BIT =1 K 0 0 1 1 L 1 0 1 1 M 0 0 0 0 +-1/2 AC CYCLE 4 1/2 AC CYCLE FIG. 9-THE BSR LAMP -CONTROL MODULE. N 1 0 0 0 The house and unit codes are easily set using FIG. 10-ONE CYCLE of a 60 -Hz waveform 0 0 1 0 0 thumbwheel switches. show4ng a superimposed control signal. P 1 1 0 0

89 PARTS LIST-COMPUTER BOARD PARTS LIST-POWER-SUPPLY BSR LINK BOARD IC14-EPROM to be programmed All resistors 1/4 watt, 5°ó unless other- All resistors 1 -watt, 5% unless otherwise noted wise noted IC11-74LS259 8 -bit addressable latch IC15-74LS373 octal latch R1,R19-200 ohms R1.R4.R14-R18--1000 ohms R2,R7,R8,R20-100 ohms R2,R5,R6-user-determined. To be dis- IC16-74LS139 dual 2 -to -4 line decoder/ multiplexer R3,R4,R11,R12,R15-1000 ohms cussed next month R6,R10-4700 ohms R3,R11,R12-10,000 ohms IC17-74LS32 quad OR gate IC18-8088 microprocessor R9-1 ohm (a jumper works fine) R7-680 ohms R13-10,000 ohms trimmer potentiome- R8-390 ohms IC19-74LSO4 hex inverter IC20-74LS123 dual one-shot ter R9-12,000 ohms R14-15,000 ohms R10-2,000 ohms Q1,Q2-2N3904 Q3 -2N3906 R16-270 ohms R13-10 ohms R17-10,000 ohms RN1-4.7K x 9 resistor network D1,D2, D4-D8-1N4148 D3 -1N4001 R18-470 ohms Capacitors Capacitors Cl-user-determined. Miscellaneous: IC sockets, PC board, mounting hardware, etc. C1,C2-10 µF, 16 volts, electrolytic C2-150 pF, ceramic disc C3,C5-0.01 µF, ceramic disc µF, ce- The following are available from Vesta C3-C8,C11-C13,C16-C20-0.1 C4,C6-0.047 µF, ceramic disc Technology, Inc., 2849 W. 35th Ave., ramic disc C7-10 µF, 35 volts, tantalum Denver, CO 80211: KIT 1-Kit of all parts C9-0.001 µF C8-.001 µF, ceramic disc needed to control 7 LS-TTL outputs, C10-27 pF C9-0.1 µF, ceramic disc monitor 7 inputs, program EPROM's, C14,C15-10µF, 16 volts, electrolytic C10-0.14 to 0.47µF, 150 volts, electroly- RS-232 serial port, and 2K RAM (does Semiconductors tic A/D (National) not include operating system-see be- IC1-ADC0804 converter C11-3300 µF, 16 volts, electrolytic buffer and line low), $99.95; KIT 2-Kit of all parts for IC2,IC3-74LS541 octal C12-500 µF, 50 volts, electrolytic full -capacity 1/O and 4K RAM (does not driver Semiconductors IC4-SN75478 seven high -current include operating system-see be- ICI-ULN2003 darlington array low), 169.95; Operating systems con- darlington drivers (TI, also Sprague (Sprague) tained in ROM: BASIC I operating ULN-2003, Motorola MC1413) IC2-TL497 switching regulator 8 multiplexer system, $12.95; BASIC II operating IC5-4051 -input analog 1C3-74LS00 quad NAND gate system, $29.95; Forth operating sys- IC6,IC7-74LS377 octal latch IC4-LM340-5 + 5 -volt regulator tem, $79.95; Assembled, tested, and IC8-74LS251 8 -input digital multiplexer IC.5-LM320-5 -5 -volt regulator ROM. 2716, 2732, or 2764. burned -in control computer with IC9-System Q1 -2N3904 BASIC II operating system, $279; 450 ns maximum access time. Q2 -2N3906 RS -232 cable, $24.95; 2716 EPROM, IC10,IC12-TMM 2016P-2 (Toshiba or Dl, D3, D5, D6, D10-1 N4001 x ns. $6.95. Add $6 for shipping, handling, similar) 2K 8 static RAM, 450 D2, 04, D7-D9-1 N4148 and insurance. IC13-Programmed EPROM (2716) T1-1122100 1:1:1 pulse transformer (Sprague) 2 3 4 6 7 8 9 10 11 T2-16 volts, center tapped, 0.4 amps. AC CYCLES (Signal ST-4-16 or similar) I I I S1-normally open momentary pushbut- 1 1 1 0 D8 08 07 D7 06 D6 05 i]5 D4 D4 D3 i)3 02 D2 131 i71 00 D 0 ton switch Miscellaneous:line cord, printed -circuit START DATA: DATA: UNIT OR COMMAND CODE board, IC sockets, heat sink for regulator, HOUSE CODE SEQUENCE - mounting hardware, etc. FIG 11-ONE TRANSMISSION consists of a start sequence, a house code, and a unit or command code. (Remember-the complete command transmission consists of two separate transmissions; the The following are available from Vesta first ends with the unit code, and the second ends with the command code.) Technology, Inc., 2849 W. 35th Ave., Denver, CO 80211: Power-supply/BSR- link kit, including all components, TABLE 4 $59.95; Assembled, tested, and burned in power supply, $109. Add $6 for shipping, handling and insurance. ADDRESS, COMMAND 04 03 D2 D1 DO DECIMAL VALUE

Unit 1 0 1 1 0 0 12 Unit 2 1 1 1 0 0 28 submillisecond timing requirements, Unit 3 0 0 1 0 0 4 BASIC cannot be used. However, the 20 Unit 4 1 0 1 0 0 transmitter driver routine has been incor- 0 0 0 1 0 2 Unit 5 porated into the BASIC interpreter. (See Unit 6 1 0 0 1 0 18 the Parts List for information on avail- Unit 7 0 1 0 1 0 10 The Unit 8 1 1 0 1 0 26 ability of the interpreter.) command Unit 9 0 1 1 1 0 14 "XMIT" eliminates all of the inconven- Unit 10 1 1 1 1 0 30 ience of developing and debugging a ma- Unit 11 0 0 1 1 0 6 chine -code routine. For example, to turn 1 1 22 Unit 12 1 0 0 on unit 6, house code M, the proper se- Unit 13 0 0 0 0 0 0 quence of commands is: 16 Unit 14 1 0 0 0 0 XMIT(18) Unit 15 0 1 0 0 0 8 XMIT(5) Unit 16 1 1 0 0 0 24 The first command alerts any units that are CLEAR 0 0 0 0 1 1 ALL UNITS ON 0 0 0 1 1 3 set to house code M, unit 6. The second ON 0 0 1 0 1 5 command turns those units on. Just to OFF 0 0 1 1 1 7 make sure you understand how to use the DIM 0 1 0 0 1 9 command/address codes, how would you BRIGHTEN 0 1 0 1 1 11 turn off house -code N, unit 6? If you study Tables 3 and 4 and our discussion, are implemented with various types of A glance at the software required to - you should see that the commands IC's that are enabled onto the data bus exercise these I/O functions will give you XMIT(151) whenever their address is present on the an idea of how easy it will be to start using XMIT(135) address bus. We will decode the I/O space the computer. For example, to set the first would do it. The first command sends the in much the same way that we did for output high we simply execute the OUT house/address code 0100/10010 (151 deci- memory. In fact we will use the other half (port,value) statement: "OUT(0,1)." mal) and the second command sends the of the same IC (IC16-b, a 74LS139 dual 2 - That BASIC statement outputs to I/O lo- house/command code 0100/00111. (135 to -4 line decoder/multiplexer) plus a few cation 0, the value 1. (See Table 5 for decimal). additional gates. (Refer back to Fig. 1 at other port "addresses.") The latch will One final point that we should make the beginning of this article.) The signal hold that value on the output line. Read- about the remote -control system is that it to ME%M will be used to enable that half of ing an input is just as easy. In this case we is a low -power communications device the decoder-that prevents an I/O device must assign the result to a variable as in operating between 10 kHz and 490 kHz from responding to an address meant for the statement: "LET A=INP(0)." Then and is therefore subject to FCC regulation memory. We will use address lines A4 and the status of the first input line, 10 deter- part 15, paragraph 15.111 (Operation be- A5 to select which of the four outputs will mines the value of A. low 1600 kHz) and 15.102 (Interference) be active (low). which states: "Notwithstanding the other Further decoding is required to separate requirements of this part, the operator of a the input devices from the output devices. low power communication device which Two OR gates (IC17-b IC17-c) provide +5V causes harmful interference to an autho- that function for those IC's that do not rized radio service, shall promptly stop have two ENABLE inputs. The memory operating the device until the harmful in- map that results from that decoding is 5 terference has been eliminated." shown in Table. 3 Digital I/O-bit-addressableI/O-bit-add The I/O systems The inputs of a control computer are Now that we have taken a look at the used primarily to sense the status (high or power-supply board, we can return to the low) of an external device. Outputs are 1 4 6 7 computer and discuss its input and output generally used to turn something on or 2 3 5 capabilities. (We briefly mentioned some off. Bit -addressable I/O allows us to act IC11 of those I/O capabilities when we talked on or read only one bit of information- 74LS259 about the remote -control system and the that bit is isolated from all of the other RS -232 port.) inputs and outputs. Although bit -ad- A computer's only link to the outside dressable I/O is neither the simplest to world is through its inputs and outputs. If implement nor the most common FIG. 12-TO TEST THE bit -addressable output type of port, you we can use this simple circuit. If you intake, for example, a personal comput- I/O, it is, in most cases, the easiest to use. stall IC4, then you can test the output at socket er, the input is usually a keyboard and the All we have to do to get our outputs is to SO4, pins 1-7. output device is usually a CRT screen. A connect an addressable latch onto data - control computer's I/O is oriented more bus line DO. By using IC11, a 74LS259, toward hardware. Individual lines can we can latch and output 8 individually - Note that the BASIC INP and OUT sense external conditions while other addressable bits to the "real world." statements are used instead of PEEK and lines control external devices. Inputs are no more difficult than out- POKE. That's because we are exchanging The number and type of those control puts. The hardware for bit -addressable in- the data in the I/O space, not in memory. lines are very important specifications of a puts consist of a multiplexer (IC8- The output line of the multiplexer is control computer-they are what deter- 74LS251) that selects the desired line that connected to data -line D7, the Most Sig- mine whether or not the computer can do will be connected to data -bus line D7. In nificant Bit (MSB) of the data bus. Be- the task that you have in mind. the case of both the input multiplexer and cause of that, we can check the state of the A microprocessor interfaces with I/O the output latch, the address lines AO, Al, input line with a single statement that tests devices in the same manner as it does with and A2 are connected to the address in- whether the data on the bus is greater than memory: An address is sent out on the puts of the IC. 127 (or less than 128). If you wanted to use address bus, data is transferred over the Before we go any farther we should data -line DO (which is connected to the data bus, and the control bus controls the remind you that the last bit -addressable inverted output of the multiplexer) you actual transfer. In many systems, I/O de- input and the last bit -addressable output would have to mask off the unused bits. vices are treated exactly as memory, in are used by BASIC for the RS -232 port. At last we can start using our computer which case they are said to be memory Do not change the state of the output or for control. As a demonstration, let's con- mapped. Memory mapping of I/O func- connect anything to the input if you are nect 7 LED's to the 7 outputs as shown in tions may be done to save hardware (addi- using a terminal for communications. Fig. 12. Also connect a single, normally tional decoders), or it may be done open, pushbutton switch between the first because the microprocessor has no provi- input, 10, and 5 volts DC. sion for separate memory and I/O space. TABLE 5 First we should initialize all LED's to The alternative to memory mapping is the off state (note that because the LED's I/O mapping, which our system uses. In Port Description are connected to +5, off is high). "Address" that case, the control bus has an additional IO FOR I=0TO6 0-7` BIT-ADDRESSABLE, line called 10/tiETvi" that determines if the SO4 12 OUT(I,1) 16 8 -BIT I/O - PORT 1, SO2 data will be transferred between the mi- 14 NEXT I 32 8 -BIT I/O - 2, croprocessor and memory or between the PORT SO3 Having 48 A/D CONVERTER SO1 turned all of the LED's off, we microprocessor and I/O. The 8088 has an will wait until the switch is turned on I/O space of 64K (which is equal to the *PORT 6 IS USED TO ENABLE RE- before going further: memory space of many microprocessors). MOTE -CONTROL TRANSMITTER. 20 LET I = INP(0) The various types of inputs and outputs PORT 7 IS USED FOR RS-232 PORT. 22 IF I <120 60T0 20

91 This will loop until the switch state is The 8 -bit parallel I/O port is the easiest quantity. Increasing the number of bits or

turned "on" . to design. All that is required for inputs is decreasing the span will increase the reso- 30 FOR 1=0TO6 to enable 8 buffers onto the data bus for lution of the result. 32 OUT(1,0) each port. That job is done by IC2 and The accuracy of the A/D conversion 34 NEXT I IC3, which are 74LS541 buffers. For out- takes into account not only repeatability, Those three lines will turn all LED's on. puts, all we have to do is to latch the status but the absolute accuracy of the output 30 FOR J=0TO50 of the data bus, for which we use IC6 and compared to the input. That is really a 40 FOR 1= 0 TO 6 IC7, 74LS377 D -type flip-flops. measure of the accuracy of the standard 42 OUT(I,0) While the byte -wide port is best suited used during the conversion process. If a 44 OUT(I,1) to data transfer, it is possible to use it for reference diode defines full-scale as 2.55 46 NEXT I bit -wise control as well-but it's not al- volts, and if that reference should drift to 50 NEXT J ways easy to isolate the single bit that's of 2.56 volts, then 2.56 volts will be required 60 GO TO 10 interest. In the case of input testing, it at the A/D input to produce a result at the involves a mathematical process called bit output of 255. That potential source of Lines 30 to 60 will blink the LED's and masking. If the output port is used for inaccuracy can be eliminated by using a then return to the switch-monitoring loop. single -bit control, a record of the state of technique called ratiometric measure- The 74LS251 can sink/source one LST- the port must be maintained in the pro- ment. Ratiometric measurements are TL load. If we are not concerned too gram so that the proper output word can made using the same source for both the much about the logic high or logic low be formed, that will toggle the desired bit reference and the transducer. Thus any voltages, then we can sink or source many but leave all of the other bits unchanged. variations will be present in both and will times that amount. The practical limits of The same simple software commands cancel out. the output drive capacity is limited to used for the bit addressable ports are used The last parameter we should consider about 15mA in the low state and about to control the 8 -bit parallel ports. For ex- is the number of channels-the number of IOmA in the high state. The output capaci- ample, "OUT(16,0): OUT(16,255)" will inputs that can be connected to the A/D ty can be increased by using IC4, an open - set all 8 outputs first to zero then to 1. The converter. Obviously with 2 A/D convert- collector Darlington array. The generous command "LET A = INP(16)" will as- ers, we can measure 2 different points. sink capacity of this device makes it sign a value to A in the range of 0 to 255 However, by equipping a single A/D con- handy for controlling relays. A snubber depending on the status of the 8 inputs. verter with an analog input multiplexer we diode is included in the package, which is can also measure several points (but not important if you will be switching any Analog inputs simultaneously). type of inductive load. Without it, the Most natural processes appear to us as There are two common methods of per- inductive kickback would cause intermit- analog or continuous -time functions. The forming the conversion. The first is called tent problems when running a program (or temperature, pressure, humidity, sound integration. The input voltage causes a it could destroy the computer outright). levels, and light levels surrounding you proportional input current to charge a ca- are analog quantities. But the measuring pacitor to a specific voltage level. The Digital I/O -8 -bit port process can convert the analog function time required to charge the capacitor is The next type of 1/O consists of 8 paral- into a discrete digital function. For exam- inversely proportional to the input volt- lel bits-often referred to as a byte -wide ple, we know that the temperature does age. The second method is called suc- UO port. The byte -wide port is a natural not change in steps. But if your ther- cessive approximation (SAR). In that extension of the microprocessor data bus mometer is only accurate to one-half de- method, the analog input is compared to and, as such, it is the most convenient gree, then the temperature will appear to the output of a digital to analog (D/A) method of transferring data to or from change in I/2 -degree steps. If you used a converter. The D/A converter is adjusted peripheral devices, such as printers, voice thermometer with higher resolution, you until its output matches the unknown ana- synthesizers, or BCD thumbwheel could extend the number of digits used to log input. The input to the D/A converter switches. express the temperature. But no matter that produces the match becomes the out- how accurate the thermometer, you can- put of the A/D converter. not express the temperature exactly. The number of tries before a match is is of A BASIC interpreter for the control In order for the computer to be able to made never more than the number computer is available (see Ordering "understand" analog quantities, they Information). BASIC I can operate on have to be converted into digital quan- ORDERING INFORMATION 26 variables, and includes commands tities. That's the purpose of the analog -to- such as: digital (A/D) converter. The following are available from Vesta Inc., 2849 W. 35th Ave., LIST NEW The first parameter used to describe our Technology, Denver, CO 80211: KIT 1: Kit of all parts RUN LET A/D converter is the number of bits the needed to control 7 LS-TTL outputs, IF FOR/NEXT result will be-the resolution of the mea- GOTO GOSUB/RTN monitor 7 inputs, program EPROM's. PRINT INPUT surement. The smallest increment or RS -232 serial port, and 2K RAM (does STOP REM change of the result is always one least - not include operating system-see be- XMIT PEEK significant-bit (LSB). An 8 -bit conversion low), $99.95; Operating systems con- POKE INP resolves to one part in 256. The next pa- tained in ROM: BASIC I operating OUT rameter is the span of the conversion. system, $12.95; BASIC Il operating system, $29.95; Forth operating sys- That is the physical range that is repre- tem, $79.95; Assembled, tested, and The BASIC II operating system in- sented by the zero and full-scale values of cludes all that is contained in BASIC I. burned -in control computer with the A/D output. Thus, if our 8 -bit convert- In addition, it can operate on 52 varia- BASIC Il operating system, $279; er had a span from 0° to 255°, each bit of 2716 bles and 1 array, and contains about RS -232 cable, $24.95; EPROM, twice as many commands. Those ex- output would represent one degree. If the $6.95; Power -supply BSR-link kit, in- tra commands include FILL, STAT, span were reduced to 125°, each bit would cluding all components, $59.95; As- DUMP, EPROM (which programs an represent 1/2°. The number of bits of the sembled, tested, and burned in power EPROM with the current program) conversion determines the resolution of supply, $109. Add $6 for shipping, han- MOD, ONERROR, and many others. the converter. The span of the conversion dling and insurance. determines the resolution of the physical

92 zero to the A/D to CABLE FROM start conversion, line 30 POWER.SUPPLY prints the result. BOARD Digital -to -analog conversion

S05 Most of the same parameters that we noted for A/D conversion also apply in D/A conversion. Although the control computer doesn't have D/A capabilities, they can be added with very little effort. As shown in Fig. 13-a, a simple resistor - capacitor network is the only hardware required. Remember the description of the SAR A/D converter? We can implement a D/A converter in a similar manner with the components we have on the board and some software. One of the bit -addressable outputs and one input of the A/D converter must be /P1 dedicated to each D/A channel. The digi- RS -232 tal output is used to charge a capacitor PORT through a resistor, and the A/D input measures the voltage on the capacitor. That measured voltage is compared to the desired value (which is stored in the program). If the voltage is too low, the output is turned on. If the voltage is too high, the output is turned off. The selection of the R -C time constant, and the frequency that the output is corrected by the program, determine the accuracy of that simple ap-

PORTI PORT 2 BIT -ADDRESSABLE I/O proach. A/D The major limitation of that approach is INPUTS that the ripple and response time of the circuit COMPUTER BOARD. Note how the 24 -pin devices are plucged into the 28 -pin sockets leaving pins 1 are directly related. If minimum and 2 empty. ripple is required, a long response time is the result. That can be avoided with a slightly more sophisticated circuit, such as the one shown in Fig. 13-b. bits of resolution. Thus an 8 -bit A/D will requirement is that the multiplexer's con- That circuit uses one bit -addressable find a match in no more than 8 tries. trol inputs be stable when the A/D con- output to charge the capacitor and another Integrating A/D's are very accurate but verter is making a measurement. to discharge it. When the voltage is cor- slow. Twelve- and 14 -bit conversions take Using the A/D converter is a simple rect, the capacitor is neither being tens of milliseconds. Successive approx- I-2-3 procedure. First, select the channel charged nor discharged. Thus, the only imation (SAR) A/D's are fast, but are not (using the 8 -bit output port). Second, contribution to ripple is the discharge cur- as accurate. Eight -bit conversions may write to the A/D to start the conversion. rent imposed by the load. The response take only a few microseconds. Third, read the result. In BASIC, we time can be made as fast as it takes the The A/D converter selected for our could write: software to decide if the capacitor requires computer is IC1, the ADC0805 from Na- 10 OUT(16,0) charging or discharging. Note that the tional Semiconductor. That 8 -bit SAR 20 OUT(32,0) circuit shown in Fig. 13-b is also shown in converter can span input voltages as low 30 PRINT INP(32) the computer's schematic (Fig. 1). The as .25 volts. Provision has been made for Line 10 selects channel 0, line 20 writes a open circles shown at diodes D1 and D2 ratiometric or absolute conversion. The (or R2) are for connection to the bit -ad- converter has true differential inputs and dressable port. The analog signal is output zero -offset adjustment. An analog multi- at TO R SOl pin 15. (That output also gets con- plexer is included in the DIGITAL ANALOG circuit that ac- OUTPUT nected to one of the A/D inputs.) commodates up to 8 input channels. OUTPUT TO C The ADC0805 is designed to be used ANALOG Digital thermometer with microprocessors, so all we have to do INPUT As an example of the simplicity and is to connect it to the data and control flexibility that smart control can provide, buses. we'll look at how we could use the control A conversion is initiated by writing TO DIGITAL R ANALOG OUTPUT 1 1 Ws. -Q OUTPUT computer to measure the temperature. (anything) to the A/D converter. The re- TO DIGITAL R The first step is to Select the transducer. sult will be available by the time BASIC OUTPUT2 F14 --9W- There are several options. We could use interprets the next program statement. TO ANALOG National Semiconductor's LM335, which INPUT The channel -select controls of the input has a linear output of 10 mV/°C. Another multiplexer (IC5 pins 9, 10, and 11) are b possible choice is Analog Devices' connected to three outputs of the 8 -bit port AD590, which has a current output that is at S02. That doesn't mean that you have FIG. 13-TWO SIMPLE D/A circuits. The circuit shown in bis also shown also a linear function of temperature. to in Fig.1, the schematic use the port, only the A/D converter-it of the computer. The values of the components can be used for data transfer. The only depend on your particular application. continued on page 132

93 Turn your computer into an automatic TRS-80 telephone dialer. TELEPHONE DIALER HOWARD BERENBON

IF YOU OWN A TRS-80 COMPUTER AND want something unique to do with your TABLE 1-PHONE DIALER PROGRAM computer system, then this project may be 10 PRINT "TRS-80 PHONE DIALER 190 GOSUB 500 what you've been looking for. With just a PROGRAM" 200 OUT 255,0 couple of components, you can build a 20 PRINT "COPYRIGHT © 1979 BY 210 GOSUB 550 telephone interface that will let a TRS-80 HOWARD BERENBON" 220 C=C -1 dial a telephone number. That may be the 30 PRINT 230 IFC=0 THEN 110 missing link to your automated telephone 40 PRINT "ENTER AN "A' TO DIAL" 240 GOTO 180 directory or your computerized burglar 400 FOR A=1 TO 90 410 NEXT A alarm. 50 INPUT A$ 60 IF A$<>"A" THEN 40 420 RETURN In to the addition interface circuit, there 70 CLS:Q =14:R =14 500 FOR A=1 TO is a short BASIC program that is pre- 80 REM DIAL THE NUMBER IN THE 510 NEXT A sented to drive the interface circuit. Since DATA STATEMENT 520 RETURN that circuit is connected to the cassette - 90 x =200 550 FOR A= 1 TO R -5 tape I/O port, you should be able to con- 100 PRINT "DIALING" 560 NEXT A nect it to just about any computer with a 110 READ C 570 RETURN cassette port and modify the BASIC pro- 120 IFC=55THEN700 700 PRINT 710 PRINT "DIALING COMPLETE gram to fit your system if you know the 130 PRINT @ x ,C 720 END port address. 140 IFC=0 GOSUB 800 150 x=x+2 800 C =10 is in The actual BASIC program listed 160 REM DIAL THE PHONE NUMBER 810 RETURN Table 1. It is a Level 2 program that drives ONE DIGIT AT A TIME 990 REM DATA STORAGE FOR PHONE the interface circuit through the remote - 170 GOSUB 400 NUMBER control relay inside the computer that is 180 OUT 255,4 1000 DATA 1,8,0,0,5,5,5,1,2,1,2,55 connected to the remote -control plug. All that is required is the simple phone interface circuit shown in Fig. 1. The circuit is ed is "55." That is used to flag the end of ten to the relay as a phone number is being connected to the remote -control plug of the phone number. dialed. When dialing is in progress, the your cassette interface cable. To dial, lift the telephone receiver and pulses generated by the program can be The interface consists of a relay, a sil- listen for a dial tone. Then type the letter heard. icon diode, one 9 -volt rectangular battery, "A" at the keyboard. The program will Though as shown in Table 1, the and a microphone jack. That's about print each digit of the phone number as it's BASIC program is limited to dialing one $4.00 worth of parts. Simply connect the dialed. phone number, it may be modified for contacts of the relay in series with the To test the dialer without connecting dialing several numbers rather easily. To green telephone wire. Since the relay is a the telephone to the interface circuit, lis - do that, the program can be used as a normally-closed type, it will not interfere subroutine, with a phone -number access with the normal operation of your tele- program written around it. phone. However, before you actually con- PARTS LIST The BASIC program simply uses the nect the telephone, you must contact your OUT command to pulse the remote -control local telephone company to insure com- D1 -1N914 diode relay, which is addressed at I/O port FE RY1-SPDT relay, 5 or 6 -volt 500 -ohm DC pliance with local -company To activate the cassette remote -control re- telephone coil. regulations. lay, the number 4 is output to port FF (see B1 -9 -volt rectangular battery 180). To the relay, a is The BASIC -language program uses the J1-phone jack line deactivate "0" OUT command to access the I/O port (port output to port FF (see line 200). R -E FF) and thus dial the phone. It pulses the cassette remote -control relay that is con- r-0 TO nected to the telephone line via the inter- TELEPHONE face circuit. (SEE TEXT) The dialer is set to dial one phone number, and print the number on the CRT RY1 screen as it is dialed. The program simu- lates the operation of a rotary dial, by pulsing out the digits to the phone interface. It will function with both rotary dial J1 and pushbutton phones. Any length phone number is placed in the DATA statement at line 1000, with commas sep- FIG. 1-TELEPHONE INTERFACE circuit can be built on perfboard. The relay contacts are connected in arating each digit. The last number enter- series with the green telephone wire. D L JThr D `21.. _ l AUTOMOTIVE exhaust -gas probe, which is inserted into the auto tailpipe; a "conversion box, " which transforms part of the exhaust into a proportional electrical signal; and a dis- EXHAUST play unit, which amplifies and digitizes the signal for easy viewing. The unit can be used either while the car is stationary, allowing you to make adjustments, or while it is in motion, allowing you to verify those adjustments under dynamic ANALYZER operating conditions. To simplify the circuitry, a commercially -available clock/timer module is Build this useful automotive test instrument and stop used for the display. It contains an LCD guessing about your cars emissions. readout, providing easy viewing under almost any lighting conditions. The mod- PHILIP M. VAN PRAAG ule's crystal -controlled timing is also used by the project's AID converter to ensure a stable timebase throughout the system. THE GROWING NUMBER OF STATE AND the gasoline. That translates to smaller An interesting side -benefit to using the federal auto -emission requirements has amounts of hydrocarbons and carbon clock module is that the unit can be used added yet another burden on just about monoxide (CO) in the exhaust. Hydrocar- as an ordinary clock or stopwatch when every motorist. Not only do you have to bons and CO are the "polluters" typically not being used to measure exhaust gas. worry about monthly payments, insur- monitored by The unit also contains low-voltage ance, and sufficient maintenance to keep govern- sensing circuitry to prevent faulty read- your car running down the road, now you ings'due to inadequate battery voltage. also have to worry about the next emissions test. Will your car pass, or Theory of operation will you have to go through the Figure 1 is a block diagram of the pri- time and often considerable ex- mary circuit functions. Exhaust -gas con- pense to have it "tuned up" and version takes place a - then retested? in thermal conductivity cell (TCC). The Worse yet, even if you a are do-it- TCC produces an electrical sig- yourselfer with an "army" of tools, nal that varies with the dif- timing lights, and dwell meters, you ference in temperature be- are still at a disadvantage with regard tween a "test" temperature to emissions tuning. Those items alone sensor exposed to exhaust are not enough to do the job, and doing gas and a "control" sen- what we did in the "good old days"- sor exposed only to am- that is, simply replacing the plugs and bient changes points, that affect setting timing and dwell, and then both sensors. "tweeking" The sen- the carburetor until the en- sors are self -heated gine runs smoothly and performs well- identically, so that just won't cut it anymore. they will be at the Indeed, often the best low -emission set- same temperature tings for your car will be quite different when no exhaust from those settings that provide the best gas is present. performance. There is simply no way to When ex- optimize those adjustments for, nor ade- haust gas quately predict the results of, an emission enters test with common service equipment. That's why you need the digital exhaust - gas analyzer that will be described in this ment test facilities. article. (More about the rela- That device is a small, easy-to -use di- tionship between combustion agnostic aid. In a general sense, it and exhaust makeup later.) Specifi- monitors combustion efficiency of the en- cally, the unit displays CO in con- gine system. That is vitally important as centrations of less than 1% to about 10%, combustion efficiency directly affects ex- and air/fuel (A/F) ratios from 14.5 down haust -gas content. More efficient com- to about 11.0. bustion means more complete burning of The project consists of three parts: an +5V

+5V A TIMER A/F CO -4 BALANCE /FUNCTION

CO /

THERMAL A/D SIGNAL EXHAUST , DELAY S1 GAS CONDUCTIVITY CONVERTER CONDITION CELL A/F TIMER INVERT/LEVEL SET MODULE

SIGNAL S3 CONDITION CLK COMPARATOR MODE +5V -*-- +5V FREQUENCY d DOUBLER BATTERY VOLTAGE

-gas analyzer. AG. 1-ALL CRITICAL circuit functions are shown i n this block diagram of the exhaust the test -sensor area, the thermal con- The unit's CO and A/F functions bear (2 seconds), and hence the test -cycle ductivity of the air changes. That affects an inverse display -relationship to each length, is determined by the nature of the heat dissipation away from the sensor, other. Thus, as the TCC output signal is counter (divide by 128) and the clock fre- thus altering the test -sensor temperature. amplified, an inverted version is also quency (64 Hz). Changes in sensor temperature cause its made available. The CO and A/F display The output signal is used as a gate to resistance to change. In this application, ranges differ for those functions, so dif- allow a certain number of timer pulses to sensor temperature never changes more ferent amplifier output -voltage ranges and be counted by the timer module for each than a few degrees centigrade, but that is levels are also provided. test cycle. That output is used to reset the sufficient. It produces enough resistance A digital display was chosen because it timer from the previous count and define change to unbalance the TCC. Because of is easier to read than an analog meter. That the start and stop of the current count. the narrow operating -temperature range, is particularly important if the unit is used The remaining task of counting and dis- sensor resistance changes linearly with while driving. Conversion of the analog playing the pulses is accomplished by the changes in temperature. sensor-signal to digital form is performed clock -timer module. Figure 3 shows the At first glance, the difference between by an A/D converter whose operation is basic timer-module operation. The mod- thermal conductivity and temperature shown in Fig. 2. Clock pulses from the ule is operated in its stopwatch mode, and measurement may not seem clear. They timer module are counted, and the results has a resolution of 10 ms. That means that both involve electrical -output changes in of that count are used by an adder to the display advances by one count every IO counters divide response to sensor-temperature changes. generate a ramp. Comparator 1 is then ms. A series of internal In a common "thermometer," the change used to compare that ramp with the analog a crystal -controlled 32 -kHz oscillator sig- in temperature is due to an ambient -air sensor-signal. The output of the compara- nal down to the desired count rate. The temperature change. In the TCC, tor is a pulse. The duration of the pulse is Stopwatch START/STOP and RESET switch- however, the temperature change is due to determined by the amplitude of the sensor es are operated electrically when power is an ambient -air thermal -conductivity signal; that is, the comparator's output is applied. change. That is, the ability of heat to dis- high as long as the ramp amplitude is The unit uses the three least -significant sipate away from the sensor is a function greater than the sensor amplitude. digits of tl-z display, with an implied deci- of heat conductivity through the gas mix- When the ramp amplitude dips below mal point between the two rightmost dig- ture. By the time the exhaust gas gets to the sensor amplitude, the comparator's its. Thus, a display of 00040 in the CO the test sensor, it has essentially cooled output goes low. The duration of the ramp mode would be a reading of 4.0%, while a down to ambient temperature. Thus, it is 00131 display in the A/F mode would be a not the of the gas that affects VARIABLE PULSE WIDTH reading of 13.1. Note that CO content is temperature (DIGITAL) OUTPUT the sensor, but rather the thermal con- expressed as a percentage, while the A/F ductivity of the gas. 0.2V COMPARATOR 2 (air/fuel ratio) is expressed, naturally Thermal conductivity of exhaust gas TCC IN REF enough, as a ratio. differs from that of air. The exhaust consists of water vapor, carbon dioxide, hy- Circuit description drocarbons in various gaseous states, and Figure 4 is a schematic diagram of the CO. The exact proportions of the different gas -analyzer circuit. The test and control COMPARATOR 1 hydrocarbon gases and CO, and their pre- sensors are precision -matched thermistor cise relationship to the thermal con- glass beads. Those beads are extremely ductivity of the mixture, is very complex, tiny, about .014 -inch in diameter. The the bead gives the unit beyond the scope of absolute measure- CLK small mass of glass ment for this unit. Fortunately, there are IN a fast response time. The beads are pre - predictable relationships over the tem- mounted in fixtures, as they would be perature ranges of the exhaust gas com- impossible to handle otherwise. (The monly emitted from a 4 -cycle internal- 64R bead leads are only .001 -inch in diame- combustion, gasoline -drive engine; those ADDER ter!) The fixtures and their housings com- can be used to help us in performing auto - 1.25V REF prise the TCC within the conversion box. A four-conductor cable routes the sensor emission adjustments. Over those ranges, FIG. 2-HOW THE A/D CONVERTER works. Note reasonable accuracy and (more impor- that for simplicity, only 3 of the 7 resistors at the signals and ground between the box and tant) repeatability can be achieved. counter's outputs are shown. the display unit.

96 tions of IC5, a dual op -amp, are used to amplify the TCC outputs, and inject a TENS OF SECONDS fixed bias between them to provide a prop-

SECONDS er operating point for the next stage. One section of an LM324 quad op - amp. IC3-a, is used to amplify the TCC TENTHS OF SECONDS outputs, and convert them to a single - ended signal. Another section, IC3-c in- HUNDREDTHS OFSECONDS verts that signal and provides level trans- lation for the A/F mode. Resistor R24 is a IÿI trimmer used to calibrate for the desired A/F ambient operating point. Final ampli- ! I:I ITI fication is provided by IC3-b; that device 32768Hz also provides the CO operating -point calibration. The fourth section of IC3, IC3- lams H d, functions as a voltage comparator, XTAL JVttlJt sensing the battery input -voltage to reg- DIVIDERS OSC DECADE DECADE DECADE ulator ICI. If the voltage drops below 7.2, START COUNTER COUNTER COUNTER TSTOP the pin 7 output goes to ground, which 32Hz RESET_T loads down the output of IC3-b, causing (TO A/D 1 CLK) ? ? the device to stop update testing. Then it's +5VJ ? time to replace the battery. Transistor Q1, and IC6 its associ- FIG. 3-THE TASK OF COUNTING and displaying the result is handled by a clock timer module. The and basic operation of that module is illustrated here. ated circuitry, prepare clock pulses for the

START/STOP_T +5V own 1/4 74C00 R14 3 4 _ 10K +5V 2 R11 5 30.9K C7 iH 1/4 74C006 03 C9 R10 2N3904 R9 .1 - 47.5K 4.64K R13 C12 132-r 8 100pF VN Ze 10K IH TM1 I A/F CO 1/4 74C00 ( TIMER R22 MODULEJ 4.87 K R12 L r S2b +5V 4,1A +5V a MA-4.7K R27 R19 NC MODE +5V 14.3K R16 R17 e 100K R23 +5V 1 6 7 10K gig 20.5 K R21 S3 2 4 30.9K 1/4 LM324 EN Vcc1 VCC2 44AA 46.4K COO R28 -. 1 9 IC3a 13 8 14 6.81K +5V + 1C3 -c 4 -Mti+3 1/4 LM324 10 S2 -a 1C3 -b VIN 1C4 VOUT- 02 R18 11 + R25 A/F TL507 C10 2N3904 20.5K R24 4.53K R26 12 ..J R20 .001 50K 1/4 LM324 10K 'R29 GNU RESET CLK C11 T1 - 12 e 100K +5V i +5V-4 11.8K 100pF W We 3 8 2 -i C4 CO TRIM A/F TRIM = ® 1 C6 ® 1/4 74000 +5V R7 01 100pF 5V 1N4148 +5V 8.45 K = R42 %4A 210K R5 LM340T-5 030 R40 4.87 K 6 POWER 15K 226K +5V 0 05 R6 o ICI +5V 5 S4 2N3904 8 4.81 K_L R31 R36 I 81 105 a C5 04 1K R8 1 _ C2 C3 22.1K > 3 ¡9V 4.87 K T.1 2N3904 BAL 1 /2 R32 R41 4 1CL7621 +5V R33 3000 143K T' T 2210 5V I R3749'46 01 YEL 22.1K +5V 2N3904 R3 GRN R43 10K e 210K r R38 1/4 74C00 5 4 ( SRI! 226K

(SR2 R34 R35 I NC 1050 1050 I R39 152K R2 _ J eRi100K 4.7K RED/ C14K BLK .05

FIG. 4-AN AUTOMOTIVE EXHAUST-GAS ANALYZER. The circuitry enclosed by the dashed box in the lower left-hand corner is located on the TCC PC -board, which is mounted in the conversion box. All remaining circuitry is housed within the display -unit cabinet. Note that many of the resistors have A/D converter (IC4) using a 32 -Hz inter- tolerances of 1% (See Parts List). mediate -countdown signal obtained from the timer module. Transistor Ql shifts the All other circuitry is housed in the dis- very subtle bridge adjustments needed to timer voltage -levels, while IC6 functions play unit. Transistors Q4 and Q5 translate "balance" the currents to the test sensors as a frequency doubler to provide the 64 - BALANCE control (R31) changes into the under ambient conditions. The two sec- Hz signal needed by the A/D converter to

97 define the two -second test interval. change the timer battery, although if the Resistors R9 and R10 determine the bottom battery retaining -clamp screw is final ambient voltage -level for the A/F left a little loose it is possible to change mode, while R11 determines the final am- the battery through the battery-compart- bient voltage -level for the CO mode. ment access lid. Those voltage levels define particular A/D Four wires have to be added to the timer pulse durations, which, in turn, define module to interface it with the rest of the particular display readouts. circuitry. Figure 7-a shows where three of The A/D output is conditioned so that it those wires are attached; shown there is can be used to control the clock module a the side of timer's PC board that's seen when the timer's back cover is removed. by IC2 and the Q2-Q3 circuit. One sec- 5/32 k---1-25/32-4»l 5/32 DIA. tion of the IC, IC2-d, along with CIO and The fourth wire is attached to the other R16 are used to differentiate and invert the 3: LC side of that board as shown in Fig. 7-b. To

form the S3 t_>1\ gain access to the timer-circuit board, pry A/D output's leading edge to \ + 5/32 + 3/16 DIA._.1 reset pulse. section of the device, DIA. off the back cover, then very carefully Another - 1/2 IC2-a, delays the A/D output from reach- b remove the four small chrome Phillips - ing the stop/start circuitry until the reset 5/16 head screws that hold the mechanism in pulse has been applied to the timer mod- place. Note the locations of the screws as ule. The IC2-b-IC2-c circuit is a "double well as the orientation of the battery re- differentiator" that provides short trigger taining clamp. You should now be able to pulses on the delayed leading and trailing lift the molded black plastic lid away from edges of the A/D output signal. Those the circuit board. Carefully solder three pulses are used to start and stop the timer. fine (30 -gauge) wires in place, using very little solder and trying to keep the wires By presenting a very high impedance to C the when the is off, and solder close to the edge of the PC timer unit switched NOTE: ALL MEASUREMENTS Q2-C11 and Q3-C12 allow the timer IN INCHES board. Next, very carefully out the spring - module to be used as an ordinary clock or FIG. 5-IF THE CABINET available from the lift stopwatch when the unit is not being source given in the Parts List is used, it is drilled steel switch strip using a pair of needle - being used for exhaust analysis. and modified as shown above. nosed pliers; note the position of the Display cabinet and timer module Caution: Before proceeding with any modification to the clock -timer module, be certain that it is functioning correctly RIDGES in all modes of operation. Once it has been modified the manufacturer will not warranty honor claims. RIDGES Figure 5 shows display -cabinet preparation details for the cabinet available mentioned in the parts from the source FRONT list. (If you purchase the complete kit, the cabinet will already have been completely a prepared.) The cutout for the LCD display can be done by first drilling a number of TIMER TOP EDGE ALIGNED WITH holes within the cutout border, then care- BATTERY COM- fully filing to eventually produce a clean PARTMENT TOP rectangular hole. The bottom of what was FLANGE intended to be a battery compartment must be cut out to provide a mounting fixture for the clock/timer module. The detail for that is shown in Figure 5-c. Figure 6 shows how the timer is modified and mounted in the clock/timer-module cabinet. Figure 6-a shows the ridges on the sides of the timer that must be filed off to allow it to slip -fit into the flanges that are formed when the battery compart-

ment is modified. You will also need to b file off a portion of the timer's case rear to NOTE: ALL MEASUREMENTS allow a 9 -volt battery to be inserted into IN INCHES the battery compartment; remove a 1V16 - inch section to a depth of 3/32 -inch as FIG. 6-A POPULAR WATCH/TIMER is used in this project. That timer's case must be modified as shown. Doing that will disable the SI and shown in a so that both it and a 9 -volt battery will fit in the display unit cabinet. How the timer is mounted in the cabinet is shown in b. S3 switches on the timer module, but their functions are replaced by the ana- side ridges are carefully filed just to the strip-it is over two small red -plastic lyzer's switches. Figure 6-b shows the point of allowing a light press fit in the studs. Then, remove the circuit board by final alignment of the timer in the display cabinet. In any event, provision must be gently lifting from beneath at various cabinet. A tiny amount of contact cement made to allow the module to be removed, points along the edge of the board. When can be used to secure the timer to the as must be done to insert or remove the PC the PC board is removed, the LCD display cabinet, but it may not be needed if the board. Removal may also be needed to will probably stick to it. If it does, care -

98 A LOOK INSIDE the exhaust -gas analyzer. The completed display unit and conversion box are shown here with their cases open.

All resistors 1%o,'/a-watt unless other- PARTS LIST Miscellaneous: PC boards, display and wise noted conversion -box cabinets. IC sockets, 9 - R1-100,000 ohms, 5% volt battery terminal clip, modular tele- R2, R12-4700 ohms, 5% phone extension cord, 25 feet, with plug R3, R4, R'3-R16-10,000 ohms, 5% R42. R43-210,000 ohms and receptacle (MCM TA625 or equiv- R5, R6, Re, R22-4870 ohms Capacitors alent), vinyl thin -wall tubing (3/e -inch I.D., R7-8450 ohms C1-05, C7-C9, C13 -0.1µF, ceramic 1 -inch O.D., 48 -inch length), copper tub- R9-47,500 ohms disc ing (3/8 -inch O.D.,'Y32-inch wall thickness, R10-4640 ohms C6, C11, C12-100 pF, ceramic disc 14 -inch length), spray bottle caps (see R11, R23-30,900 ohms C10-.001 µF, mylar text), alligator clip, cable strain -relief (5/,6 - R17, R18-20,500 ohms C14-.05 µF. ceramic disc inch mounting hole), silicone glue, Velcro R19, R20-100,000 ohms Semiconductors strip (11/2 inches wide by 3 inches long), R21-46,400 ohms IC1-LM340T-5 or 78M05 +5 volt regula- double -sided carpet tape, 30 gauge wire, R24-50.000 ohms, miniature potentiom- tor 8 -conductor ribbon cable, knobs, hard- eter, li.lear taper, vertical PC -board 102, IC6-74000 CMOS quad NAND ware, etc. mount gate R25-4530 ohms IC3-LM324 quad operational amplifier The following are available from PVP R26-10.000 ohms, miniature potentiom- IC4-TL507C A D converter Industries, P.O. Box 35667, Tucson, AZ eter. blear taper, vertical PC -board 105-ICL7621 DCPA dual operational am- 85740: Etched and drilled epoxy -glass mount plifier PC boards for display cabinet and con- R27-14,300 ohms Q1-Q5-2N3904 NPN silicon transistors version box for $14.95; SR1, SR2 sen- R28-6810 ohms D1 -1N914 or 1N4148 general purpose sor pair for $22.95; PC board set, both R29-11,500 ohms diode cabinets (not drilled), timer module, R31-1000 ohms, miniature potentiome- SRI. SR2-G126 precision matched ther- front panel decal for display cabinet, ter, linear taper, panel mount, with mistor pair (Fenwal Electronics, 63 and modular extension cord for SPST switch (S4) Fountain St., Framingham, MA 01701) $49.95; complete kit of all parts (except R32-300 ohms, miniature potentiome- TM1-timer module, model U01 sport glue and battery), including pre -drilled ter, linear taper, vertical PC -board stopwatch (Armitron Corporation, 29-10 cabinets for $98.95; completely as- mount Thompson Ave, Long Island City, NY sembled, calibrated, and tested unit for R33-221 ohms 11101) $129.95. The above prices are postpaid f134, R35-105 ohms S1,S3-SPST momentary normally open in the continental U.S. Arizona resi- R36, R37-22,100 ohms pushbutton (C & K 8631 or equivalent) dents add 5% sales tax. Readers of Ra- R38, R40-226,000 ohms S2-4PDT rotary, panel mount dio -Electronics are invited to send a R39-152,000 ohms S4-SPST potentiometer switch, part of SASE to the above address to receive R41-143,000 ohms R31 free updates on this project, along with B1 -9 -volt battery user tips as they become available. fully separate it from the board, noting its removed. (That is important because there very carefully scrape the green lacquer orientation and setting it back into the is usually no pin identifications on those coating off the PC pattern at the point case exactly as it was before the board was displays.) Using a jeweler's screwdriver, continued overleaf

99 BATTERY (+1

S1 S3

SOLDER HERE NOT ON PAD

17-

3-15 16 INCHES PADS

FIG. 9 --THE COMPONENT SIDE of the double -sided display PC board. It, too. is shown full sized. FIG. 7-FOUR WIRES must be added to the timers PC hoard as shown above.

21.2 INCHES

FIG. 10-FULL-SIZED FOIL PATTERN for the TCC board. That board mounts in the conversion box.

Display -electronics construction Full-size PC -board patterns are shown in Figs. 8, 9, and 10. We recommend using PC boards, as that will considerably reduce construction and debugging time. It will also help eliminate the possibility of any high -impedance -leakage paths or spurious -signal pickup. The use of IC sockets is recommended as those allow easy IC removal/replacement should servicing ever be required. Full-size foil patterns for the double - 3 15/16 INCHES. sided display PC board are shown in Figs. 8 and 9. If you choose to etch your own FIG. 8-THE FOIL SIDE of the double -sided display PC board is shown here full sized. It's parts - board, and cannot provide plated -through placement diagram will be shown next month. holes, you will have to solder all component leads on both sides of the board. In shown in Fig. 7-b. Do not touch any of the Next, set the PC board into the case addition, you will have to insert a wire pads that mate with the LCD display. along with the switch -contact strip. Re- into all pads that do not contain compo- Using a very fine -tipped soldering iron, insert the molded black plastic lid and and nent leads, then solder those feed through and a small amount of solder, tin both the the screws (do not over tighten), dress the wires on both sides of the board. exposed copper foil and the wire to be wires up out of the way, and make a note Figure 11 is the parts -placement di- attached. Do not allow any solder or flux of the wire colors for later identification agram for the display board; Fig. 12 is the to contact the pad located below the trace. when connecting them up to the gas ana- parts -placement diagram for the TCC Touch the wire and the iron to the point lyzer's PC board. The timer's back cover board. Note that the four -conductor cable that was tinned to attach the wire. will not be used in the cabinet. on the TCC board (Fig. 12) is installed on

100 the foil side. Be careful to orient all IC's, sistors in place, trim the leads flush with cover will fit without binding at the switch diodes, and polarized capacitors as the solder mounds. Next, install the IC shaft clearance hole. When satisfied, re- shown. Use a 25 -watt iron with a fine sockets, making sure that the notch, or move the PC board and complete the con- pointed tip, and .030 -inch solder. dot, on one end of the socket is aligned tact soldering. One point should be made here about with pin 1. Note that the IC's themselves, The four-conductor cable interface be- the resistors. Note that the majority are with the exception of ICI, are not to be tween the display unit and the conversion precision 1% units. Such resistors are now installed now. As IC1 is a voltage reg- box is made using a modular telephone - available from a number of sources, in- ulator, it is not socketed. Instead, solder extension cable with plug and receptacle cluding Digi-Key (Highway 32 South, PO that device directly to the board at this assembly. Cut a 9-inch section of the ca- Box 677, Thief River Falls, MN 56701). time. Then mount the diodes making sure ble at the plug end, and use that to connect A less expensive alternative for those who that they are oriented properly. Next, in- the PC boards. Figures 11 and 12 show have well stocked junkboxes is to test stall the capacitors beginning with the how the boards are interconnected. The more common 5% resistors with a DMM physically smaller types. Next, mount the color scheme indicated is not mandatory, until ones with the precise value called for trimmer potentiometers: R24, R26, and but following it will minimize any chance are found. R32. Then mount transistors Ql-Q5. of confusion. Note that the receptacle is Study Figs. 11 and 12 before starting The function switch (S2) shaft must be mounted on the conversion box and wired construction of the boards, and decide trimmed to a 3/8 -inch length. When that to the TCC board. Doing that allows the upon a method of attack for inserting the has been done, mount it on the PC board, conversion box to be disconnected from components. Although individual styles but only after the cabinet top has been the display unit when not in use. differ, the following sequence should drilled and can be used to check switch Figures 11 and 12 show how the boards work well. The idea here is that by se- alignment. That is important since the are interconnected. The color scheme in- quencing the parts installation according switch cannot be moved once it is sol - dicated is not mandatory, but following it

TO will minimize any chance of confusion. CLOCK Note that the receptacle is mounted on the MODULE conversion box and wired to the TCC A board. Doing that allows the conversion B1 box to be disconnected from the display Y 1---- unit when not in use. U cnIm ti Turning to the off-board components,

S4 use small -gauge, color-coded wires for POWER the connections to S1 and S3. Twist them rather tightly to prevent spurious ignition - noise pick-up that otherwise could occur with some automobiles. (The noise pick- R31 up would cause erratic timer triggering BALANCE 1430 and occasional faulty display readings.) S1 START/STOP When construction of the display board 0 -CR C7- op_ is complete, clean off all solder -flux resi- -R16- --C10 due with isopropyl alcohol or commercial R2/ --R12- -1129- spray flux -remover. If using a commercial I I -R28- I -R13-- flux remover be sure to read the directions Ril R4C14 V- oO S3 as some of those are harmful to plastics. ICE RESET ( -RS --T C13 Conversion box preparation R23 R3 Figure 13-a shows the conversion -box -R2-- --R15-, preparation details for the box available GND(B K) --R14- -i+ `R7- 17741 from the supplier mentioned in the parts TO GNDIRED) -R43- 01 C5*,- R41- - - C12 CONVERSION list. Also shown is the probe and tubing CTL(YEJJ -R42- -R40 - 0 BOX -7 e3 assembly (Fig. 13-b). is TESTIdifiN) -R36- -R39-- The probe built R37- --R38- using 3/8 -inch outside diameter (O.D.) j4R33. copper tubing, with an alligator clip add- C5 C1 ed to make sure that the probe remains in R26 R24 fi 112 the auto -exhaust pipe when it is placed C A,F BRIDGE there. A 48 -inch length of 3/8 -inch I.D. FIG. 11-PARTS PLACEMENT DIAGRAM for the display aoard. Study the board carefully before beginning construction. (Inside Diameter), 1/2 -inch O.D., vinyl tubing connects the probe to the con - to the height of the components, several dered in place. If it is crooked when in- similar components can be inserted on the stalled, it will not allow the top to be F-----CTL(YEL) board before the board is inverted and the attached properly. Set the switch into the TO GND(RED) DISPLAY E - - - - parts soldered in place. That should speed board (noting the rotational alignment GND(BLK) things up a bit. shown by the tab position in Fig. 6-b). It BOARD E---- I TEST(GRN) I First, install the horizontal -mount fixed may be necessary to straighten some of --I 1/4 -watt resistors, slightly bending the the contacts before it can be smoothly 11 leads after insertion to avoid misposition- inserted. The switch should be inserted in ing when the board is inverted for solder- the board to a depth such that about /16 - SR1 SR2I R34 R35 ing. (To help in troubleshooting, should it inch of the solder contacts protrude out become necessary, orient the resistors so beyond the bottom of the board. Then two contacts and FIG. 12-THE FOUR -CONDUCTOR CABLE is in- that all the first bands point in the same lightly solder one or stalled on the foil side of the TCC board. Note direction. That also makes the project temporarily install the PC board in the that Fig. 10 shows an "X-ray" view of the board, look a lot neater.) After soldering the re - cabinet bottom. Check to see that the top not the foil -side as was stated last month.

101 tube. Thus, gas will be allowed into the 12 box only at the top and bottom of the ALLIGATOR CLIP washer, and to a small degree through the outer sides. r- Battery operation Two self-contained batteries are used by the unit. One is a hearing -aid type 1.5 - volt cell. The other is a common 9 -volt transistor -radio -type battery. The 1.5 -volt cell is used in the timer module and its life expectancy is Cover one year. 2.7/16 The 9 -volt battery powers all of the remaining circuitry. Current drain is rather high due to the required thermistor heat- 1/2 ing. Therefore, the unit should only be 1/2 turned on when exhaust measurements

l ' 21/32 5/16 DIA are needed. Also, when replacing the battery, be sure that the unit is off (to prevent 11/2 1-1/16 damage). 5/32 DIA 3/8 DIA 21/32 Checkout and calibration pro- 1-1/8 5/16 DIA The following calibration/test cedures are performed with the probe ex- i 3 9/16 NOTE: ALL DIMENSIONS posed to ambient air-conditions only. Do 47/16 IN INCHES not allow exposure to exhaust gas at this time. Double-check all connections and component orientation. Do not install the INSERT WASHER HERE 1/16 ICI, WHEN ASSEMBLING IC's into the sockets yet. (Only (SEE TEXT) which is soldered in place, should be installed to this point.) -01,1/414- 1/8 - - If you haven't re -installed the timer bat- x 2 tery yet, do so now, and verify that all that all of the timer's functions operate as de- (a). and tubing assembly (h). and a tube FIG. 13.-DETAILS for preparing the conversion box the probe scribed in its owners booklet. With no stub (c). external power applied to the unit, all timer functions should be just as they version box. (Note that if you purchase mate dimensions as shown) should then would be normally. If that is not the case. the complete kit from the source men- be glued to the board over the sensor as- do not proceed until you have isolated and tioned in the parts list, all cutting and semblies. Try to center the caps around corrected the problem. Try disconnecting drilling will already have been done.) the sensor fixtures. Silicone glue may be the four wires from the display PC board. A 2 -inch copper tube stub (see Fig. 13- used, although 3M windshield adhesive If operation returns to normal, then some- c) is needed to attach the vinyl tubing to (available at automotive -parts stores) is thing is probably miswired in the Ql, Q2. the conversion box. Crimp a '/s-inch even more effective. Apply the glue to the or Q3 circuitry. If timer operation is still length of one end in a vise to obtain the mating surfaces only. When the caps are faulty, then either the wire connections on flattened dimensions indicated. Then drill in place, coat the outer cap and the board the timer board are bad (for example, sol- a 5/32 -inch hole where shown. Insert a No. surfaces with additional glue to be certain der bridging across two circuit paths) or 6 flat washer (3/s -inch O.D., 'A2 -inch of a good seal. Once the glue is firm, melt the timer module is bad. thick) into the flattened portion when as- a hole into the test -sensor cap where Before connecting the conversion -box sembling as discussed below. Flattening shown in Figure 14. (The hole should face cable to the display unit, apply power via of the stub and inserting the washer cre- the side of the conversion box that con- S4. Check the voltage at IC12. It should ates a controlled inlet aperture. That aper- tains the strain-relief/cable assembly.) be + 5 volts. Leave the power applied for ture limits the exhaust -gas flow rate into Holding a I/4 -inch diameter screw with a a few minutes, then touch ICI. It should the conversion box, ensuring adequate pair of pliers, heat the screw with a candle be just slightly warm, not hot. If all is gas cooling before exposure to the TCC. flame and use it to melt a hole through the well, remove power, connect the con- Velcro strips can be used to allow at- plastic. The cap/board assembly should version -box cable, and install the remain- tachment of the conversion box to the then be silicone glued to the side and ing IC's.. Then set the BALANCE control automobile. First, glue the "fabric" por- bottom of the conversion box. Be sure to (R31) and trimmer potentiometers R24, tion of the strip to the back of the con- use ample amounts of silicone glue R26, and R32 to their midpoint positions, version box. Then, double -sided carpet around the control sensor, as it is vital that and set the FUNCTION to the co position. tape can be applied to the mating Velcro no exhaust gas be allowed to reach it. If the timer had been in the normal strip for attachment to the bumper. (Never Assemble the tube stub as shown in clock mode, you must change it to timer stick the tape onto a painted portion of the Fig. 14 using four 6-32 nuts to space the mode by holding S3 depressed for a few car, as the paint is likely to come off when stub from the side edge. Don't forget to seconds until the display changes to all removing the strip later on.) place a No. 6 washer inside the flattened zeros. Now re -apply power. After several Figure 14 shows the component and tube end before tightening the outside seconds, the display should begin to re- board placement within the conversion 6-32 nut. When the four "spacer" nuts are spond to the initiation of tests about every box. As shown, the sensors should be snug, tighten the outside nut with a small two seconds. mounted 1/4 -inch above the PC board. wrench or pliers until the tube end is com- If the word LAP appears on the display Plastic spray -bottle caps (with approxi- pressed against the washer inside the (below the two smaller digits on the right), 102 that means the count/reset sequence is out TO DISPLAY of step. That may occasionally happen UNIT after power up. Simply depress the TIMER switch one time. That should clear the counting abnormality within two or three test cycles.

Now proceed with the calibration pro- TEST CHAMBER cess, as follows. Again, be certain that GAS INLET HOLE there is no exhaust gas near the conversion (SEE TEXT) box, and that its temperature is stable. Also, orient the conversion box as shown DRAIN HOLE in Fig. 14. (That is the orientation that will 1/4 be used during actual exhaust testing.) SR2 1. Connect a DVM between the dis- (TEST) play-board pads for the green and yellow leads to the TCC board. Adjust R32 for a CAP DIAMETERS: reading of exactly 0 volts. There will be 13/16 (NARROW ENO) some settling time required, so leave the SR1 15/16 (WIDE END) (CONTROL) DVM connected for about 30 seconds. (4) 6-32 NUTS BOARD DIMENSIONS: 2. Adjust R26 for a display of 4.0% 1 X 2-1/2 Take your time in doing that step as it is rather critical. Make the adjustment in small increments until the reading changes with each test cycle. If movement in one direction doesn't produce a display change, go back to midrange and try the other direction. When you do start seeing #6 WASHER INSIDE TUBE a change, continue to adjust, but in even smaller increments, until the display reads 4.0 consistently on several subse- TUBE quent tests. STUB ALL DIMENSIONS 3. Switch to the A/F mode, and adjust IN INCHES R24 for a 13.1 display. Follow the procedure outlined in the previous step. That completes the checkout and cal- FIG. 14-THE TCC BOARD is mounted inside the conversion box. Note that all exhaust tests are made ibration process. The settings of R24, with the conversion box oriented as indicated by the arrow. R26, and R32 should not require readjust- ment under normal circumstances. The BALANCE control should give you enough ing off the car. Do not attach the probe begin to change in response to each test of an adjustment range to compensate for until after the balance operation described cycle. any subtle variations due to component below has been performed. The unit uses the three rightmost dis- aging or imbalances at particular ambient Before the unit can be used, two things play digits for readout, with an assumed temperatures. must be allowed to happen: One is that the decimal point between the rightmost two WARNING: Exhaust gas is poi- engine must be allowed to reach its nor- digits. Thus, a 134 display in the A/F mode sonous! Do NOT ever perform any ex- mal operating temperature (about 10 min- indicates a 13.4 air/fuel ratio while a 036 haust -gas tests in an enclosed or poorly utes in mild weather), and the other is that display in the co mode indicates a CO ventilated area! Even being inside a car the test unit must be allowed to stabilize content of 3.6%. with the windows rolled up is no as- (about 1 minute). If you warm up the car To activate the unit, rotate the BALANCE surance of safety. While the system itself while allowing the unit to stabilize, be control from its off position to about mid- is designed so that gas is sampled and sure that no exhaust gas is allowed to range. As explained above, allow a brief converted to an electrical signal outside reach the conversion box until after the warmup period. That allows time for pre- the car, exhaust gas can seep into the car in balance operation is performed. Also, heating the TCC sensors, and generally many other ways. Do NOT take chances! never start the engine while the probe is allows the system to become acclimated inserted in the tailpipe, as the initial surge Setup to ambient conditions in the test environ- of exhaust is extremely `dirty," and could ment. Once the display stabilizes, adjust The first step is to attach the conversion coat the TCC, altering the unit's accuracy. the BALANCE control for a reading of 4.0 box to the rear-bumper area. Choose a A small piece of tape may be placed over in the co mode or 13.1 in the A/F mode. position that allows the tubing and probe the conversion -box gas -inlet stub and When the engine is running at normal to reach the exhaust tailpipe without drain hole during warmup to ensure that operating temperature, insert the probe stretching or sharply bending the tubing. exhaust gas will not enter at that time. into the tailpipe, and attach the tubing to Also, observe the mounting direction as In use, all functions are displayed when the conversion box. There will be a very outlined earlier. Velcro strips may be used the timer is in the stopwatch mode. If the brief response lag -time encountered as to attach the box, but they may not be timer is in the clock mode, depress the the display changes to reflect the thermal suitable for all applications. Other alter- MODE switch for a few seconds until the conductivity of the gas sample. (Note that natives may be necessary, such as mask- display reads all zeros. That can be done a new sample test is performed about ing tape. An especially sturdy mounting whether or not power has been applied. In every two seconds.) It is normal for some is not needed unless the unit is to be used fact, if power is not applied, the unit can fluctuation "drift" in adjacent readings, while driving, in which case adequate be used as an ordinary stopwatch. Once particularly if the engine is idling rough, means must be provided to prevent a power is applied and the unit is placed in or if the engine system routinely changes change of position or the device even fall - the STOPWATCH mode, the display should idle speed, timing, or carburetor mixture

103 ture too lean. The few pennies saved in in response to engine temperature. fuel vapor to carburetor). stored fuel will be more than offset by subse- If your automobile has a catalytic con- 4. EGR (routes portion of exhaust having to repair burned valves, verter, accurate readings can best be ob- back to carburetor). quently combustion tempera- tained by sensing the exhaust gas before 5. PCV (Positive Crankcase Ventila- due to excessive 14.0 the converter. While some autos have a tion system-routes "blow -by" tures. Air/fuel readings above about less port available for this testing, it will prob- gases back to carburetor, and al- indicate a lean mixture (i.e., more air, to crankcase). about 12.0 in- ably be necessary to remove the exhaust - lows fresh air enter fuel) while readings below 6. Spark -timing advance (three com- gas recirculation (EGR) valve and insert dicate a rich mixture. mon types: deceleration -vacuum The advantage of using the unit while the probe at that point in the system. (It -gear -shift control, transmission driving is to verify A/F carburetor settings will then be necessary to close off the control, and engine temperature and general carburetor/accelerator pump EGR line to the intake manifold to ensure thermostat -vacuum control). under actual operating condi- accurate readings.) The catalytic convert- 7. Thermostat -engine coolant (higher response er changes much of the hydrocarbons and temperature thermostats being tions. At cruising speeds, with a light CO into water and carbon dioxide. That used). engine load, the A/F reading will nor- "new" gas/vapor mixture presents a dif- Proper carburetor operation is vital to mally be a little leaner (by about .3 or .4) ferent composite thermal conductivity to minimizing exhaust pollutants. All pas- then when the auto is stationary. After the TCC, thus affecting accuracy. sages and internal/external components sudden, brief acceleration the reading must be clean, and gaskets must be secure should diminish considerably, then grad- Adjustments. to prevent air or fuel leaks. Once that has ually rise back to nominal. Service data When making adjustments, be sure to been accomplished, the various adjust- for your auto should provide specific load allow time for the display to respond. It ments must be set to the manufacturer's readings. time for the engine system to stabil- instructions. Those adjustments typically takes Suspicious readings ize on the new setting(s), and then it takes include float, choke, throttle, and air/fuel a short time for unit to respond to the mixture, but may include other things, Sooner or later, you will probably en- different exhaust -gas content. If the unit is such as multi -carburetor synchronization. counter readings that just don't seem to to be used on more than one vehicle dur- While "in the old days" simple cookbook make sense. There can be many sources to ing a session, allow several minutes for adjustment procedures could be given (for of inaccuracy, but first it is important remaining exhaust to clear the conversion example: "tighten down mixture screw, determine the general cause. There are box before connecting it to the next vehi- then back off 3 turns..."), today that is three general causes to consider: the auto- cle. When making adjustments that typ- just not possible. The importance of using mobile. the setup, or the unit itself. Once the specific ically have a broad range, it is best to a CO meter and strictly following the auto the general cause is found, make small incremental changes, pausing makers' adjustment instructions is no bet- problem is much easier to track down. after each and then noting the display. ter exemplified than with the carburetion One common auto symptom is the car- having any That method makes it easy to "zero -in" setup. buretor-mixture control not on the optimum setting without losing effect on CO readings. That is a "normal" control; that is, getting things so far out of Readings occurrence if the carburetor needs over- adjustment that the engine dies, or that it As mentioned earlier, auto makers typ- hauling. What has happened is that block- in have is difficult to return to the original set- ically provide emissions -adjustment in- ages or leaks the carburetor tings. formation in the engine compartment. disrupted normal operation enough to The following emission -related com- That information often includes CO and make the relatively minor mixture -screw ponent topics are intended for general in- A/F readings that should be attainable if changes ineffective. It is also possible that formation only. Specific adjustments for all systems are functioning properly. the air filter is clogged. To verify, note the your auto should be made in accordance Tune-up manuals will also provide that A/F reading, then remove the air-cleaner with the auto makers' prescribed meth- information. Of course, it is also impor- element, re -attach the air-cleaner cover, ods. Occasionally, emissions tuneup pro- tant to know your state's prescribed max- and retest. If A/F ratio is now more than .2 cedures and data will be included on imum CO limits for your make, engine, or .3 higher than before, the filter proba- decals in the engine compartment. Other- and year auto. Those limits vary consider- bly needs replacing. wise, consult an appropriate service man- ably. Another source of potential trouble ear- ual for details. It is a good idea to take a In Arizona, for example, a 1972 Ford from the automobile, as mentioned CO reading before making any repairs or Pinto with a 4 -cylinder engine is allowed lier, is "swamping out" of the TCC due to adjustments so that you can later measure 6% CO maximum. A 1981 Dodge Aries, an unusually dirty exhaust blast, such as your progress by "before/after" compari- also with a 4 -cylinder engine, is only al- that which would occur if the engine is son. lowed 1.5% CO maximum. A 1973 12 - started with the probe attached. Swamp- adjustment is It is wise to begin by checking the igni- cylinder Jaguar XKE is allowed 5.5% CO. ing can also occur if an that causes a very tion components: replace, clean, or re - Some auto types seem to be rather amena- made, while testing, man- gap spark plugs as needed; set point dwell ble to achieving even very stringent re- dirty exhaust. Swamping typically is and ignition timing to manufacturer speci- quirements, while others (like the Jaguar ifested by a suspiciously low CO reading, fications; check spark plug wires; and mentioned above) just barely squeak by or a suspiciously high A/F reading. (In clean/inspect distributor cap. relaxed requirements, and then only after extreme cases, the CO reading may "at- Equipment added to modern auto- considerable effort. In general, however, tempt" to reach zero. When that happens, mobiles to reduce emissions include (in 10- or 15 -year-old cars should be able to the display will stop updating entirely. until the part) the following items. They should be deliver about 3%-4% CO, while the very The display will remain "frozen" inspected, cleaned, replaced, or adjusted latest cars should be down to about 1%. TCC clears-typically 10-15 minutes is re- as recommended by the auto maker. Air/fuel ratio measurements are es- after the offending gas mixture way that is to 1. Air -inlet temperature damper pecially meaningful when making car- moved.) The best to correct (routes preheated air to carburetor buretor adjustments. Once again, it is shut off the engine and allow the TCC to during engine warmup). important to consult the manufacturer's "breathe" ambient air for 15 minutes or 2. Air pump (pumps air into exhaust data for recommended procedures and so. Another solution is to deliberately manifold area to improve combus- readings. It can be injurious to the engine force a rich mixture situation (such as by tion efficiency). valve system, for example, to set the mix- temporarily blocking part of the air intake 3. Charcoal vapor-evaporator (routes

104 to the carburetor) until the CO percentage needs to again "breathe" ambient air for times. There always are reasons, but swings up a few percent (or the A/F read- several minutes; then reset the BALANCE sometimes they can be quite difficult to ing is down considerably); then allow nor- control. determine. In states such as Arizona that mal air flow and check the reading after A particularly perplexing symptom is allow "conditioning mode" testing if the about a minute. If it returns to the same where the display is erratic; that is, where initial test fails, the auto is run at acceler- super-low CO, or super-lean A/F, then the unit is obviously performing tests, but ated engine speeds, in gear on rollers, for that's most likely the real situation, unless with significantly different readings on about 30 seconds and is then retested- one of the remaining two possible trouble each trial. Verify that swamping or im- often with dramatically lower readings. areas is at fault. proper setup is not influencing the read- Everything is exactly the same as before, If the setup is suspected, re -check the ings by shutting off the engine and except that some of the excess combus- setup conditions mentioned earlier. It is observing the readings over several min- tion byproducts (built up, perhaps, during important that all conditions be met, such utes, making sure that the conversion box the long wait in line to be tested) have as positioning of the conversion box and remains in the same position and ambient been blown out. allowing sufficient time for the system to temperature. If the readings remain erra- The message here is: Don't be alarmed stabilize before balancing and then begin- tic, there is a problem with the unit's elec- if any particular readings appear to be ning the test. It is also possible that ac- tronics. But, if the readings stabilize, somewhat different from the last readings curacy could be affected if a significant there is either something wrong with the taken. To best determine the state of ex- temperature change occurs in the con- setup or you have a really weird exhaust haust emissions, you really need to aver- version box area after balancing has been mixture. age the readings. In particular, take note performed. An example of that might be if The whole business of emissions test- of subtle changes in test conditions that the sun came out from behind a cloud and ing is very tricky. Those of you who own can affect the results. Paying attention to significantly changed the ambient tem- "marginal" cars (remember that Jaguar those details will improve the overall perature conditions around the conversion we mentioned?) know what we mean. usefulness of the unit and rectify the emis- box. Although immune to subtle changes Each emission test can bring new sur- sions from your automobile, thus improv- in ambient temperature due to the "con- prises-sometimes good, sometimes ing the quality of air we breathe-and trol" sensor presence, very large tem- bad. The same car, with the same tank of that's what it's all about! R -E perature-changes can cause a shift in the gas, with the same emission settings, can balance point. To re -balance, the TCC produce different readings at different

Typewriter word counter until the space bar is hit. Hitting the space bar opens the space -bar Hall - HERE'S A PROJECT THAT CAN SAVE YOU goes to logic I. effect switch, which in turn resets the some when time you need a manuscript The switches are connected to % of RS flip-flop. Subsequent spaces are of a specific length, such as fora school a 4043 RS flip-flop. After the circuit has ignored until the next keystroke is project, a classified advertisement, etc. been reset, the output from that flip- entered, and the entire cycle is repeated. It will keep track of how many words flop is at logic I. At the first keystroke, If the space bar and a key are struck at you've typed, and display the total. The the output from the Hall -effect switch the same time, the flip-flop's output is circuit uses Hall -effect switches (Sprague goes to logic 0, pulling the flip-flop's logic I. and the next keystroke incre- UGN-3020T, or equivalent) to detect output to logic O. The output from the ments the counter. keystrokes and spaces. flip-flop drives the MC 14553 three - When the count reaches 999, the next The Hall -effect switches are sensitive decade counter. That counter is nega- negative transition will clear the counter to the presence of a magnetic field. In tive -edge triggered, so the transition of but set its overflow high. That overflow this project, permanent magnets are the flip-flop's output from logic 1 to output is latched by a second flip-flop, used to turn the switches on and off. logic 0 increments the counter. The lit of the 4043. driving the display's When the magnet is near the switch, counter's BCD output is then fed to the most significant digit (the 1 on the dis- the output from the switch is logic 0; 4511, a BCD -to -7 -segment display de- play) on. The procedure then repeats, when the magnet moves away, the coder/driver, which in turn controls the for a maximum count of 1999 words. switch opens and, because of the 31/2 -digit LED display. For this circuit to work, the Hall - 10,000 -ohm pull-up resistor, the output Each subsequent key stroke is ignored effect switches and the magnets must be mounted inside the typewriter itself. PE2MAKIEOT MAGNETS (SEE TEXT) One switch and magnet should be 1-9V mounted so that they are close together normally, but move apart when rn any key t9V V is struck. The second switch 10K 1311 IG V V V and magnet should be mounted so that they KEY III. q 3112- I Seowe IGIT move apart when the space bar is hit. 15 114 9N STRILCE +4V MG {e 4043 14553 45,, QNA d MULTI- The switches and magnets are mounted 2 C PLExED 4 a VW- 7 b ED using epoxy glue. Both sets of switches i Oh v 9 7 DISPLAr and magnets should be positioned so 14 that the thick side of the switch (the SPACE M SD side opposite the dot) is normally near IN914 the magnet's south pole. You can ALL 1K power the circuit any way HALL -EFFECT you wish. One good way would be to SWITCHES look use a wall -plug transformer with a 9 - (SPRAGUE (A -302.0T) Ik ti 144043 .,vv------volt output. You could also use a 9 -volt battery. If you do that, you may want to devise a display blanking circuit to FIG. 1 extend battery life. -Lam Dighera

105 SLIDING -TONE DOORBELL

HAVE YOU EVER BEEN STARTLED BY YOUR own doorbell? I have heard some door- Z 2i 51 + 42 bells that are so harsh and startline that IZG D2 ZK GI IN911 2,4 521(. they are sure to wreck anyone's nerves. 20 vs. .o4af is not of that type-at R2 But my doorbell ID -3 look least not any more. IN911 c3 81L But if your bell is of that type, don't RS 8+ 20,«F RA- 59K2 despair. I'll show you a way to prevent 50K SOK 2N5219 l' t your quiet home from being disturbed. c2 You can replace your harsh -sounding, R3 I OO I Ox F nerve-wracking bell with what I'll call a K "mild dose of sound stimulation." When the doorbell is pushed, you'll hear a low FIG. 1 tone that will "slide up" to a higher frequency. decrease. Thus, whenever R00 or Cl de- also by R5, the total resistance again de- increase. creases, and the oscillator's frequency Figure 1 shows the sliding -tone door- creases, the frequency will bell circuit. It's made up of two main First, assume that Si is closed and R2 again increases. parts: an AF (Audio Frequency) oscillator has been adjusted to produce a pleasant, If you're not satisfied with how the things and a variable resistance. low -frequency tone. Capacitor C3 will "bell" sounds, there are several The frequency of the AF oscillator is charge through R6 until it reaches such a you can do. First, if you want to change determined by two factors. The first is the voltage that will cause diode Dl to con- the tone variation, feel free to try different value of the coupling capacitor, CI. The duct. When that happens, the value of values for R2, R4, and R5. And if you speed of the tone, second is the value of the resistance con- RBG is paralleled by R4. Thus, because want to vary the sliding of R6. nected between the base of Q1 and the total resistance RBG decreases, the then you can try different values ground. That resistance, which we'll call output tone slides up in frequency. Capac- As with the rest of this easy -to -build not crit- RBG, is equal to (R1+ R2) R3. itor C3 will continue to charge until the circuit, the transistor types are When either of those two factors in- voltage across D2 and D3 causes those ical. Feel free to experiment!-Tseng C. creases, the frequency of oscillation will diodes to conduct. Then RBG is paralleled Liao

PLANT-WATER MONITOR

That's where this project idea comes in. It's a plant -water monitor and is used to test the moisture of the soil at root level. When the soil is moist, an LED glows. If 25 the moisture falls below a certain predeter- 3'1o 3,`1K Le_DI mined level, the LED begins to flash. IF there is still less moisture, the LED turns 7 T off. the device is 24 The schematic diagram of RZ shown in Fig. I. It can be built on a small 47K 10k piece of perforated construction -board \---v-1cl T120o and housed in a small plastic case -or ex- s perimenter's box. The probes are two

DI slender metal rods. They should be tinned r_2 S. Iv to prevent corrosion. For convenience, you can mount the probes on the case. ZENER Nort_ FoLARizED Calibrating the monitor is easy. Just connect the battery and insert the probe into a container of dry soil. Set RI to its maximum value then reduce that resis- FIG. 1 tance until the LED begins to flash. The range over which the LED flashes before going out is adjusted using R2. ONE OF THE MOST CRITICAL FACTORS IN A how do you know when to water them? If you wish, you can reverse the opera- plant's well-being is the amount of water it Just looking at the soil can be misleading tion of the circuit. That is, you can have receives. A plant that receives too little, because it's the moisture at the root level the LED off when there is enough water, or, for that matter, too much water will that's critical. Thus, soil that's dry at the and on when more water is needed. That's soon be in poor condition. As for house top of the pot could be quite moist at the done by simply switching the positions of plants, you, their owner, determines how root level and adding more water could R1 and the probes in the circuit.- much or how little water to give them, but put the plant in jeopardy. Sreekumar, J. CABLE - TV DESCRAMBLING Learn the theory behind cable -TV signal -scrambling techniques by investigating a descrambling circuit. FRED MEANS

IT IS ESTIMATED THAT BY THE END OF THIS used today: the inband gated -sync meth- intervals, the picture tube's electron beam decade, almost ninety percent of all od. We will explain the theory behind is cut off as it retraces horizontally or households will be wired for cable televi- inband gated -sync scrambling/descram- vertically.) Those synchronizing pulses sion. One reason for cable TV's popu- bling; and to further help you to under- are among the most important parts of a larity is the excellent reception of local stand and become familiar with the standard TV signal. They are picked up television broadcasts that it provides. An- theory, we'll discuss a descrambling cir- by synchronizing circuits in the television other reason is that several premium (pay) cuit that you can experiment with. set and are used to stablize the picture. channels-that cannot be received with- Figure 1-a shows part of a normal, de- out cable service-are offered. To prevent How is a signal scrambled? modulated, television signal that you unauthorized persons (or non -subscrib- Before we can understand what a would see, for example, after the TV's ers) from viewing those premium chan- scrambled signal is, we have to take a look video -detector stage. The horizontal - nels, the signals are often scrambled. at a normal signal. Such a normal signal blanking pulse can be seen in its proper That is, the video signals are processed so contains horizontal- and vertical -syn- place in the signal. (The vertical -blanking that they can't be viewed on a normal chronizing pulses that are sent during the interval-when the electron beam snaps TV-even one that is wired for cable- horizontal- and vertical -blanking inter- back to the top left corner of the screen to unless some device is used to decode or vals respectively. (During those blanking begin a new picture field-is not shown.) descramble them. There are several techniques - VIDEO that cable WHITE LEVEL TV companies are now using to scramble their signals. In this article, we'll take a look at one of the more popular methods 111111111111111111i1I I1IIIII1I11IIII11 u IIIIIIIIIIII BLACK LEVEL HORIZONTAL BLANKING _ PULSE COLOR WARNING SYNC The legality of the use of privately HORIZONTAL BURST owned or built devices to receive or de- SYNC code cable TV broadcasts is currently a PULSE subject of much controversy, debate, and a litigation. In certain instances, the TV cable com- WHITE LEVEL panies and the FCC have taken the position that receiving and decoding cable -TV 1..1 111111111111 Z!i"F 111111111111111111111 11111 Zf 1111111111111 broadcasts without paying for them is BLACK LEVEL "theft of service." This article merely explains how one H E---1 decoding device functions and is constructed. Prior to your using such a device, however, you are advised to obtain - HORIZONTAL -BLANKING independent advice as to the propriety of INTERVAL

such use based upon your individual cir- /J cumstances and jurisdiction. FIG. 1-THE INBAND GATED -SYNC scrambling method moves the horizontal -blanking pulse of a normal signal (a) into the video portion of the signal (b).

107 Now we can explain how the inband gated -sync scrambling method works. In SCRAMALBLED IIIIII1!1111I1IIIII) Illhhiilllliidl IIIIIII--- BLACK LEVEL that scrambling method, the level of the SIGN -u, horizontal -sync and colorburst information is changed so that it is the same as that of the video information, as shown in Fig. 1-b. (The suppressed information is still within the signal's 6 -MHz bandwidth, thus the word "inband." The "gated - sync" portion of the term means that during the horizontal -blanking interval, a gating signal is used to change the level of CORRECTION SIGNAL the signal.) BLACK LEVEL Because of the change (about 6 dB) in the level of the horizontal -blanking pulse, h the TV's horizontal- and color-synchronization circuits do not pick up the pulses HORIZONTAL they need for synchronization. Therefore, BLANKING the picture that you see is not stable-it is INTERVAL to it, thus restoring out of horizontal sync and the picture's FIG. 2-WE CAN DECODE A SCRAMBLED SIGNAL by adding a correction signal color is also poor. The audio is not af- the horizontal -blanking pulse to its proper location. fected, though. Unlike many of the over- pulses are on the -air scrambling schemes, the audio is carrier of the video signal. And because MHz), the horizontal -sync not scrambled in the inband gated -sync the sound carrier is 4.5 MHz above the 59.75 MHz, and so on. we horizontal -sync method; it is simply passed through. picture carrier, we know where to look for Once extract the the hidden sync pulses. For example, pulses, they can be used, along with the Descrambling the signal channel 3, whose picture carrier is at aid of some time -delaying circuits, to The correction We can see that to descramble the sig- 61.25 MHz, has its sound carrier at 65.50 create a correction signal. can then be added to the input signal, it will be necessary to place the hori- MHz. Therefore, if you wanted to decode signal and zontal -blanking and -sync pulses back signals from a cable system that used nal to put the horizontal -blanking where they are sup- into their proper location. But first we channel 3 as its output, you would have to -sync pulses back we want to do is to add must locate the hidden pulses. In the in - look for the horizontal -sync pulses at posed to be. What voltage to the input signal but band gated -sync signal, the 'horizontal - 65.50 MHz. However, for a cable system a small DC video not during sync pulses are modulated on the sound that has its output on channel 2 (55.25 only during its portion, A MRF-901 may be substituted for 02. D2 TOKO NO. 144LY-120K T1 and T2 rated at 1 microHenry. 1N914 OUTPUT Q1 C5 R7 C6 L1 ' 12µH 2N3904 .001 27052 .001 J2 C19 AAA. 10/16V 01 + R1 R2 R8 C8 200K® 3.9K 3952 .001

TOKO N0. R19 K5552 BKATZ AXX 2K

C9 C1* .001 R3 5pF +12V 100K MICA INPUT C2 C4 MC1330A1P .001 8.2pF C18* 1L .11 02 NPO .071µH BF 0.85 1113 C22 TOKO R5 C3* R4 2K C12 NO. E520 HN-3000023 39052 5pF 10K MICA I.1 1.001 +12V ITOKO NO. C10 T1 BKAN-K5552 AXX NORMAL/SCRAMBLED .01 R9 T R10 5152 68052 .0 Si 4Ye C13 POWER C11 R 15 Q3 R11 .001 C20 1 C7 T.001 10K 2N3904 L `L 470/16V .001 27052 .L ° J3 - + Z 1116 13 V+12 ' 27K VOLTS 14 IC3 0 IC2 Ic1s R18 7812 C14 74123 3.0056 R12 22K .0015 15 12052 *ses . C21 + l R14 16 2 47Q/35VT - 10K 10 -C17 01 2E' l C15 1N5231B 1.001 T.001 IC2 *SEE TEXT

FIG. 3-THE SCHEMATIC of the descrambler is shown here. Note that the values of some components should be changed for operation at different frequencies. The descrambler can be used even with cable-ready sets. See the text for information. 108 HORIZONTAL and C3 to 10 pF, and changing the value HORIZONTAL of r-- VIDEO SYNC C18 to 130 pF. SYNC PULSE PULSE The output of IC1 (pin 5) is the demodulated 03 ON LEVEL horizontal -sync pulses, as shown in Fig. 4. Most of the video on pin 5 ICI ' \Ilnl of \\\pulllllllllllllllllllllllllllll should be filtered by C13 and the input of FIG.4-THE OUTPUT OF ICi (pin 5) should have a minimum amount of video between the sync pulses. Q3 (provided that the video is below the level that is needed to turn Q3 on). the blanking interval. That process is pass only the audio portion of the input However, there will still be a small shown in Fig. 2. The result of the de - signal. Potentiometer R1 can be used to amount of video present between the hori- scrambling process should be the original vary the level of the signal at the output of zontal -sync pulses. That video has to be waveform shown in Fig. 1-a. the tuned circuit. Adjustment may be nec- reduced-which can be done by fine-tun- essary because the inputs to the decoder Circuit description ing L2. (The result of too much video at from different cable -TV systems often are pin 5 is false triggering of IC2. That The schematic of a circuit that will do at diffèrent voltage levels. shows up as streaking horizontal lines what we want is shown in Fig. 3. First After being amplified by Q2 and passed across the picture.) we'll look at the power supply. The circuit through the C1 -T2 filter, the signal is fed When watching non -scrambled sig- can be powered by an AC adapter that has into ICI, an MC1330AIP low-level video nals, we do not need the sync pulses from an output from 14 to 18 volts DC at 100 detector. (That signal contains the audio pin 5 of ICI. Therefore switch SI is mA. The 7812 regulator, IC3, provides 12 information of the input signal-where provided to shunt the sync pulses to volts DC to the rest of the circuit. The the sync pulses are hidden.) The tuned ground. When the switch is open, input and output of the regulator are fil- circuit (L2 and C18) associated with IC! is however, the sync signals are sent to tran- tered by capacitors C20 and C21. Zener also tuned to the frequency of the audio sistor Q3, which is used as a buffer. From diode D1 is used to provide +5 volts for carrier of the input signal. That is, 65.50 there, the horizontal -sync signals are sent IC2, a 74123 dual retriggerable monosta- MHz for channel -3 operation, 59.75 to IC2, a 74123 dual monostable multi - ble multivibrator. MHz for channel -2 operation. So, if oper- vibrator. Transistor Ql provides a small amount ation on channel 3 is required, the value of We use IC2 to form the horizontal - of gain to the input signal-that compen- C18 must be 68 pF. Operation on chan- blanking interval from the demodulated sates for any losses caused by the de - nel -2 requires C18's value to be 82 pF. sync signals. (The horizontal -sync scrambling pulses circuit. Transistor Q2, a By changing the resonant frequency of from IC1 are not the proper pulse width BFQ85, is also used as an amplifier. But it the tuned circuits, the descrambler can be that we need.) The two R C timing cir- will amplify only signals a of certain fre- used at other frequencies than those of cuits associated with IC2 (at pins 6 and 7 quency. That frequency is determined by channel 2 or 3. For example, if your TV is and at pins 14 and 15) determine the pulse the setting of two tuned circuits. The first "cable -ready" you would want to de - width of the output. Potentiometer R17 tuned circuit is made up of T1 and C3. Its scramble the output of the tuner section. can be adjusted to "fine tune" the output resonant frequency will be set to shunt the The output of the tuner is usually at 45.75 for the pulse width that is needed -11 video portion of the input signal to MHz (video carrier). The audio carrier is microseconds. ground, while letting the audio portion of therefore located at 50.25 MHz. The Once the proper pulse width is obtained the signal through. The other tuned circuit tuned circuits could be adjusted for those for horizontal blanking, the signal from is made up of T2 and Cl. That is set to frequencies by changing capacitors Cl pin 5 of IC2 is fed to a voltage divider made up of R10 and R11. (The value shown for R11 works well when the input signal's level is between 50 to 70 millivolts. However, because different cable systems have different signal levels, it may be necessary to increase or decrease the value of R11.) From the voltage divider, the signal is fed to diode D2, where it is used to raise the DC level of the input signal-but as we mentioned before, only during the video portion of the signal. During vertical blanking and horizontal blanking, no DC level is added to the signal. In effect, by increasing the DC level on the video-and only during the video-we are returning (with the help of the DC -restoration circuit in the TV) the horizontal -blanking pulse and colorburst information to their proper location on the composite -video signal. Building the circuit For those of you who want to experiment with the circuit we have been describing, we have included foil patterns for a double -sided board in Figs. 5 and 6. Although a double -sided printed -circuit 4 INCHES board is used, plated -through holes are FIG. 5-THE COMPONENT SIDE of the decoder board. Note that there are only 7 connections to be not necessary. That's because there are made on this side of the double -sided board, so plated -through holes are not necessary. only seven connections that need to be

109 need to be placed through holes in the board. You can simply place it flat on the PC board and solder the leads to the foil (tack solder). Note that the dot on the parts -placement diagram indicates the collector lead. (Note that there is a dot on the transistor's package, too.) When we assembled our prototype, we mounted it in a plastic box and used an %s -inch jack for the input from the AC adapter, and F - type connectors for the signal input and output. The connectors that you use in your setup depend on what type of plug your AC adapter has, and what type of RF connectors you need to connect to your TV and cable converter.

Checkout and alignment Do not hook up this device unless -you are properly authorized to do so. As we continue, we will presume that you have received the proper authorization. The first step is to plug the output from the AC adapter into J3. Using a voltmeter, check for + 12 volts at the positive side of 4 INCHES C2O. Then check that you have + 5 volts FIG. 6-THE FOIL SIDE of the decoder board is shown here. at pin 16 of IC2. The next step is to tune to a scrambled

J1 J2 station and connect the circuit between a INPUT 0 OUTPUT C> 7/1 cable -TV converter and your television. (Jack J1 is the input jack, and J2 is the jack for output to your TV.) Make sure that switch Si is in the open position (not shorting the output of ICI to ground). Then adjust potentiometers RI and R17 to approximately the "12 o'clock" position. -C7- R9 -R18- -R11- To set the coils in their approximate loca- -R12- I " tion, turn the slugs counterclockwise until ____>41 -C14 - the top of the slug is even with the top of the coil. Then turn the slugs clockwise as -C17- R10 follows: T1, 21/2 turns; T2 and L2, 3 turns. With those adjustments in their approxi- 1C2 C15 mate locations, you can go on to the fine tuning of the circuit. -C16- Using an oscilloscope, check the input -R16- signal level. If it is between 50 to 70 R14 millivolts, adjust R1 so that you have 9- C18 L2 R17 about 4 volts on the collector of Q2. (As I mentioned previously, the value of RI1 C19 may also have to be changed.) If the input -R19- signal is higher than 70 mV or lower than 50 mV, you will have to increase or decrease the voltage on the collector of Q2 proportionally. Next use an oscilloscope to look at the signal at pin 5 of IC1. Adjust the 3 coils to keep the level of the video to -fic2,) J3 NUwUn a minimum between the horizontal -sync FIG. 7-PARTS-PLACEMENT and otf-board connections are shown here. Note that the jacks used pulses. (See Fig. 4.) When adjusting the depend on your power source and RF connections. (We used a ,.B -inch jack and F -type connectors.) coils, adjust them only % turn at a time. Those adjustments are critical and have to soldered on both sides. Figure 7 is a parts - the one on the side of the transformer with be accurate. If you see streaking horizon- placement diagram for the board. Mount the part number- on each has to be cut tal lines through the television picture at the components as close to the PC board off. Be sure that when you install the this point, it's because you are getting too as possible. When installing the electroly- transformer, the pin that you cut does not much video and are false firing IC2. tic capacitors (C19, C2O, and C21), be contact the PC -board's ground trace that Now, using an oscilloscope, look at the careful to check for proper polarity. The runs under it. signal at pin 5 of IC2. Adjust R17 until the same holds true for the two diodes. To provide the regulator (IC3) with a signal has a pulse width of 11 micro- Transformers Tl and T2 must be modi- heat sink, it should be mounted with its seconds. When the pulse width is correct, fied so that they will fit into the holes on flat portion soldered to the board's foil. you will be correctly gating the video sig- the PC board. That is, one of the pins- The leads of transistor Q2 (BFQ85) do not continued on page 132 ELECTRONICALLY HARRY L. TRIETLEY in this article, we'll take a look at thermocouples, thermistors, piezoelectric crystals, and other types of transducers. We'll also look at some techniques that will help you use transducers more effectively.

ELECTRONIC MEASUREMENTS HAVE BE - Position measurement come a part of everyday life. It can even be The best known and understood posi- seen in your car, where micro- tion transducer (see Fig. 1) is the potenti- processors-using electronic sensors- ometer. Precision single -turn potentiome- control fuel -injection and ignition sys- ters can provide accuracy (linearity) to tems. Even your auto -exposure camera 0.5% and better, and repeatability to uses electronic sensors. Electronic ther- 0.1%. They are available with wirewound, mometers and weather stations are be- metal -film or conductive -plastic ele- coming commonplace, as are microcom- ments. Multiturn potentiometers offer the puter -controlled appliances. And those same specifications; they are used for ap- are just a few examples of where trans- plications where rotation may exceed 360 ducers are used in consumer applications. degrees. Potentiometers are available In science and industry, the need for trans- with different, nonlinear responses- FIG. 1-THIS POSITION ducers for precision measurements, log- such as logarithmic TRANSDUCER provides and square -root. a signal proportional to the extension of a stain- ging, and automatic control also abound. Because of the potentiometer's high less steel cable. In this article, we'll take a look at some electrical sensitivity, amplification- and of the most common transducers and their readout -circuitry may be simple, or even be one percent or better, its end -to -end applications. We'll see how they can be nonexistent. An ohmmeter might be used resistance is typically within only ± 3 to used to measure temperature, pressure, to read the potentiometer's resistance di- ± 10%. Its contact resistance may add flow, force, vibration, liquid level, con- rectly-but that's not recommended. further readout inaccuracy. A better ap- ductivity, and other variables. While the potentiometer's linearity may proach is to connect a known voltage 1

VOLTAGE matches the decrease in the other in the across the potentiometer and use a high OUT linear region. If temperature or other in- impedance voltage readout to measure the -tom the primary -to -secondary wiper position. By properly selecting the fluences affect feedback alters the AC source to voltage, the output may be read directly as ratio, 10 100 5p compensate. inches, millimeters, degrees of rotation, 10 50 1t10 Although LVDT's require a bit more etc. Or, the voltage may be fed to an A/D POSITION CORE circuitry than potentiometers, they're still converter for computer input or data log- (% NOMINAL RANGE) ,. straightforward to use and offer ging. relatively Being essentially fric- Potentiometers are not limited to mea- good sensitivity. E- they offer long life and excellent suring angular and linear position-they tionless EXTENDED EXTENDED resolution and repeatability. LVDT's with can be used to sense any variable which RANGE RANGE built-in oscillator and amplifier circuitry can be converted to position. For exam- REDUCED REDUCED available to provide DC -in, DC -out ple, pressure often is sensed by using a LINEARITY LINEARITY are operation. bellows that is linked mechanically the FIG. 2-AN LVDT produces a voltage output as a Like potentiometers, LVDT's are used wiper of a potentiometer. A bimetallic function of the core position. sense position, pressure or any other element will transform temperature to to which may be transformed into position, while liquid level may be mea- variable Also like potentiometers, sured using a float. Companies that pro- position. may be custom designed for spe- duce such assemblies commercially often LVDT's cific applications. use custom -designed potentiometer elements rather than standard products. Strain gages Transformer transducers The strain gage is a simple, no -moving - parts device that transforms strain, force, Another widely used position trans- or pressure directly into electrical resis- ducer is the Linear Variable Differential tance. To understand its operation, con- Transformer, or LVDT. The LVDT is an sider stretching a length of wire. As it is electromechanical device that produces stretched, its length will increase and its an output proportional to the displace- FIG. 3-AN LVDT. Note the separate, free -mov- cross-sectional area will decrease. There- ment of a separate, movable core. It con- ing core. fore its resistance will increase. If the wire of three coils around a cylindrical sists isn't stretched too far (past its elastic lim- form. The primary is wound at the center it). it will recover. Thus we have a trans- of the form, with a secondary wound at phase -shifted null signal. Another prob- ducer that provides a resistance that goes either side. A free -moving rod -shaped lem is that the output sensitivity may up or down with applied strain. core inside the coil assembly links the change with temperature due to changes strain -gage elements consist of primary's magnetic flux with the two sec- in the resistance of the windings. Most metal foil or wire arranged in a zig- ondaries. The circuit shown in Fig. 4 solves those etched zag pattern for maximum sensitivity. Fig- If the secondaries are connected series - problems. The secondaries' outputs are 5 shows two examples. The foil usu- opposing, the net output of the LVDT will rectified, filtered and fed to an amplifier ure is bonded to a high grade plastic or be the difference between their voltages. that responds to their difference (a dif- ally flexible film and etched, much like a That voltage will be zero when the core is ferential amplifier). The outputs are also other flexible circuit board. Wire may be sim- at the center, or null, position. When the fed to a summing amplifier that controls ilarly bonded or it can be stretched un - core is moved, the induced voltage in the the amplitude of the primary voltage between support points. coil toward which the core moves in- source. As the core moves toward second- bonded in- Many conductor alloys and backing creases, while the opposite coil's output ary 1 or 2, that secondary's output are available (depending on the drops. As shown in Fig. 2, that produces a creases while the other drops. The materials differential voltage output that varies lin- differential amplifier responds to both early with changes in the core position. magnitude and direction; also, the ampli- the phase changing by 180° as the core fier's output at null is zero. Meanwhile the moves from one side of null to the other. summing amplifier sees a constant signal, Straight-line LVDT'S with linear travel since the increase in one output exactly from under 0.1 inch to one-half or three- quarters of an inch are most popular, (see DIFFERENTIAL AMPLIFIER Fig. 3) but devices with travel up to 24 AC inches are available. Linearities from 0.5 SOURCE operate to 0.1% are normal. Units that FIG. 5-STRAIN GAGES can be made from foil from 115 volts at 60 Hz are available, but (as in a) or from wire (as in b) operating frequencies from 1 to 20 kHz at one to ten volts are more common. Aver- 4 range re- age sensitivity for each 0.001 inch travel is OUTPUT sensitivity and temperature strain -gages, which ex- a few millivolts (per volt of input), but quired). Silicon long -travel units are less sensitive. hibit much higher sensitivity (typically of wire or foil) are also An LVDT may be read out by con- AMPLITUDE thirty times that necting its secondaries series -opposing CONTROL available. Unfortunately they also have and measuring the output AC voltage. higher temperature coefficients and more That's less than ideal, however, for several limited temperature ranges, requiring reasons. First, the AC readout will read care in application. SUMMING gages usually are connected in a upscale regardless of which direction the AMPLIFIER Strain Wheatstone -bridge configuration such core moves. Second, even when the core FIG. 4-THIS LVDT circuit provides a linear, is at the center position, the output will bidirectional, regulated readout of core posi- that the bridge imbalance varies with not be zero-there will be a residual, tion. strain. Since the sensor's resistance is low

112

1 and changes generally less than a percent LOAD CELL ASSEMBLY streams, the liquid height behind a spe- with strain, the bridge output is small. REGULATOR cially -shaped notched dam known as a I- R1 Amplifying electronics must have high weir is used. (The relationship between gain and good DC stability: High-grade +VOLTAGE +SENSE height and flow depends on the shape of op -amps or instrumentation amplifiers are -VOLTAGE the notch, but is not linear.) normally used. Alternately, the bridge - SENSE may be excited from an AC source, using Piezoelectrics AC amplification followed by phase -sen- R Quartz and other natural and manmade sitive demodulation for measurement. z crystals generate a small voltage between The bridge voltage should be kept low to OUTPUT their opposite sides when stressed. There- minimize o errors (resistance shift) due to R2 fore they're ideal for making force and resistive heating of the sensor. pressure measurements. (Microphones Achieving precision results DIFFERENTIAL with strain ---i AMPLIFIER and phonograph cartridges are examples gages requires a fair degree of mechanical of other ways that effect is used.) Al- sophistication. Electrical sophistication though useless at DC, such devices are also is needed; for example, look at Fig. L_ J superior to strain gages for measuring 6. That system uses temperature -sensitive FIG. 6-A COMPLETE STRAIN GAGE bridge high -frequency vibrations or impulses resistors (RTI and RT2) to compensate for compensates for temperature shifts in zero and with fast risetimes. changes in zero and sensitivity caused by sensitiviity. A four-wire regulator is used to compensate for lead -wire resistances. Piezoelectric crystals are not con- temperature changes. Fixed resistors (RI ductive; they act as a high impedance AC and R2) are used to trim sensitivity and source. More precisely, they act as an AC - zero. Temperature -related errors are voltage source in series with a small ca- caused not only by the strain gage ele- pacitor. A change in the voltage, AV, ments, but also by mechanical expansion causes a small charge, AQ, to flow on or and contraction of the measuring assem- off the plates of the capacitor. Outputs of bly. piezoelectric transducers are generally Strain -gage resistances usually are low specified as picocoulombs per unit force enough (typically 350 ohms) that the re- (for example, picocoulombs per psi). sistance of the leads between the regulator Voltage amplifiers for piezoelectric trans- and the bridge have to be considered. (The ducers must have a very high input imped- resistance of the leads can lower the ance (just as amplifiers for microphones bridge voltage, reducing its sensitivity.) or phono pickups must). The capacitive When long leads are necessary, errors loading due to input cables can become a may be eliminated using a four wire reg- problem. ulator. Such a regulator uses an extra pair A circuit that minimizes those prob- of wires to sense and control the regula- lems is the charge amplifier shown in Fig. tor's output directly at the bridge's input. 9. In that circuit, an op -amp (or other FIG. 7-STRAIN GAGE load cells and pressure This is not necessary if long leads are not high-gain, high -impedance inverting am- used. sensors are available in a wide variety of config- urations, some of which are shown here. plifier) is provided with CF . a negative - Many companies offer a wide variety of feedback capacitor. The high negative strain -gage load -cell assemblies for force feedback holds the voltage at the input to ORIFICE and weight measurement, and pressure - DIFFERENTIAL near PLATE PRESSURE zero-nearly all the charge from the sensor assemblies to measure liquid and CLAMPED CELL transducer flows onto CF . Also, since the gas pressure. Examples are shown in Fig. BETWEEN input voltage is PIPE zero, the cable capaci- 7. FLUID Typical specifications for such assem- FLANGES FILLED tance stores no charge, and so causes no blies include 350 -ohm bridge resistance, IR:) PRESSURE TAPS errors. 10 -volt maximum excitation, 0.1 to 0.5% nonlinearity, and a full-scale sensitivity of 2 or 3 millivolts per volt of excitation. Load ':. e capacities range from a few pounds FLOW to a hundred tons or more; similarly, pres- PIEZOELECTRIC A SENSO R sures from a few to hundreds of thousands >¢W W of pounds p_ per-square -inch may be mea- J sured. Such devices are used to measure wcc OUTPUT CC 6 weight, fullness of a bin (using the weight DISTANCE of the bin), liquid level (using fluid pres- FIG. 8-PLACING A RESTRICTION in a pipe sure at the bottom of a tank), barometric causes a pressure drop that can be used to

I I pressure, and many other variables. measure flow. I The flow rate of liquid or gas is also L_ _J measured using strain gages (or, for that sembly designed to measure differential matter, any other pressure sensors). By pressure. With such an arrangement the FIG. 9-A CHARGE AMPLIFIER completely placing a restriction in a pipe (as shown in flow rate is proportional to the square root transfers the piezoelectric sensor's AC charge Fig. 8) and measuring the pressure drop of the output signal to the feedback capacitor, produc- pressure difference, requiring a ing a proportional AC output voltage. The feed- across it, the flow velocity may be deter- square -root amplifier in the electronics. back resistor (which should be large) stabilizes mined. The most common restriction is There are other arrangements that are the DC output level. the orifice plate, a thin metal plate that has also used to measure flow rates. For exam- an opening that's smaller than the diame- ple. the pressure difference between the The voltage on the feedback capacitor ter of the pipe. Pressure -measurement inside and outside radii of an elbow - is given by AV = AQ/C. Therefore the taps, at precisely located points above and shaped band in the pipe can be used to charge amplifier's output is 1/C volts per below the plate, are connected to an as - calculate the rate of flow. For large, open coulomb. This output is directly propor - 113 tional to the AC force or strain on the Small discs and beads are commonly piezoelectric crystal. The design of a suit- used for precision temperature measure- able amplifier involves a tradeoff between ment. Discs, generally under 0.1 inch in using a large feedback capacitor (for high diameter, may be ground to a precise re- negative feedback) and using a small ca- sistance and are available with accuracies pacitor (for high gain.) up to ± 0.1°C or better. Since their con- Accelerometers can be made by construction usually involves soldered connecting a mass to a piezoelectric crystal. nections and epoxy coatings, their service Any change in velocity causes the mass to temperatures often are limited to 150°C push or pull on the crystal. producing an (302°F) or less. Glass -encapsulated discs output proportional to the rate of accelera- are available for use at higher tempera- tion. Accelerometers are used to study the tures; they provide superior stability plus a vibration and shock response of mechan- hermetic seal. Bead thermistors may be ical designs and to measure shock, accel- much smaller and generally operate at eration and vibration in engines and higher temperatures. Because of their vehicles. They also are used to monitor small size and method of construction, seismic vibrations as well as the vibra- they cannot be ground to tolerance. (Se- tions of structures such as bridges. A crys- lected or matched units may be ordered, FIG. 11-THERMISTORS AND OTHER tempera- be mounted directly between however.) tal may also available in a wide variety of is easy be- ture sensors are an object under test and the point of im- Designing with thermistors sensor assemblies. pact to measure peak forces during impact cause their high sensitivity means that testing. The crystals themselves are fairly precise measurements may be achieved in screw rugged and capable of withstanding high using ordinary components. At 4% per- mounts. thermistors mounted peak loads. degree, a one -percent error is equivalent heads etc. Piezoelectric sensors are especially to only 0.25°C. Figure 10 shows two basic Thermistors offer a variety of uses be- They valuable in measuring explosions, blasts circuits: a Wheatstone bridge and a paral- sides temperature measurement. as -compensat- and pressure surges. Depending on their lel network. The bridge provides an out- often are used temperature ex- design, response times to one microsec- put that increases with temperature, while ing components in electronics. One the temperature - ond are possible. Applications include the parallel network's resistance de- ample is compensating meter-coil. gun and ammunition testing, engine -cyl- creases with an increase in temperature. induced changes in a copper used inder and even atomic -blast measure- When designing thermistor circuits, the Large, nonprecision thermistors are resistance ments. Industrial measurements range power dissipation should be kept low (0.1 as current -inrush limiters (their them up). from plastic injection molding pressure to mW or less) to avoid self-heating errors. drops as the current heats washer -shaped thermistors moni- the impact force of punch presses. Large, tor temperature in such applications as motor overtemperature protection. Temperature measurements uses for Perhaps the most common Resistance thermometers transducers is to measure temperature. generally are Electronic temperature -sensors fall into Resistance thermometers fine -gauge wire three classes: resistive (thermistors and made of a length of other insulating) wirewound), thermocouples, and inte- wound on a ceramic (or sensors are grated circuits. support. Surface -temperature and made of wire or foil sandwiched between The resistance of both thermistors a b wirewound sensors changes with tem- flexible plastic films. FIG. 10-THERMISTOR CIRCUITS. The Wheat- Platinum is the most common metal perature-but that's where their similarity increases with temperature, stone bridge output use nickel, cop- ends. Thermistors are highly sensitive while the resistor network's resistance de- used, but many sensors need not (typically 4%I°C), nonlinear devices with creases. per and other metals. (Platinum element uses only negative temperature coefficients and a be expensive: a typical wire.) range. Wire wound sensors are The bridge may be made to read tem- 20 inches of 0.001 inch diameter narrow IEC, less sensitive (typically 0.4%/°C), fairly perature differentials by replacing R2 International -standard (DIN, have a resis- linear, have positive temperature- coeffi- with a second, identical precision ther- ASTM) platinum sensors 138.5 ohms cients. and are wider-range devices. mistor. Such a circuit is useful for measur- tance of 100 ohms at 0°C and ing heat -exchanger or solar -collector at 100°C. Common temperature ranges go Thermistors performance or for measuring the dif- down to - 200°C (- 328°F) and up to Thermistors are formed by mixing to- ference between a wet- and dry-bulb ther- between 500°C and 800°C (932°F and gether various powdered metal -oxides, mometer. 1472°F), with a tolerance of ±0.25°C at forming them into desired shapes, and If the circuits in Fig. 10 are changed by zero. Other resistances, ranges and toler- firing them at temperatures around adding a series resistor-thermistor com- ances are available. Wirewound sensors 1000°C (1832°F). They may be formed by bination in parallel with the thermistor, generally are cylindrical, under 0.1 inch pressing the powder into discs, washers, then the bridge and the parallel network diameter, one half to one inch long. rods, squares, sheets, or other shapes be- may be made to provide linearity to 0.2°C Resistance thermometers have a lower fore firing. Another method is to dip plati- and better over temperature ranges as sensitivity and lower resistance than ther- num -alloy wires into a slurry of the oxides wide as 100°C. Calculation of the best mistors. For example, 100 -ohm platinum and fire directly to form small beads. The combinations of resistors and thermistors sensors change by 0.4 ohms per degree oxides form a semiconductor material is not easy, but some thermistor manufac- C-one ohm equals a change of 2.5°C whose resistance decreases as tempera- turers offer preselected component sets. (4.5°F). Therefore the lead wires or cables ture goes up. An almost limitless variety Thermistors often are mounted in probe used with them can introduce appreciable of sizes, shapes and tolerances are avail- assemblies or other housings for protec- errors. To avoid those errors it is common able, with resistances at room tempera- tion. Figure II shows a variety of assem- to use readout circuits which either ignore ture running from 100 ohms to a megohm. blies such as sheathed probes, surface or compensate for lead resistance. Figure

114 12 shows one such circuit, which requires

four interconnecting leads. In that circuit, COPPER a constant current is fed through one pair 1ó TO MICROVOLT of leads, and the voltage drop across the COPPER ò READOUT sensor is read via a second pair. The ener- THERMOCOUPLE gizing current does not flow through the measurement leads, so the readout sees only the I x R volt drop across the sensor itself. LIQUID -FILLED Figure 12 also shows a method of com- GLASS TUBES pensating for the nonlinear temperature response of platinum. (Platinum's sen- ICE/WATER sitivity drops slightly at higher tempera- BATH (0°C) tures.) A small amount of positive feedback causes the current source to increase at higher temperatures, offsetting the drop in sensitivity. With proper design, linearity as good as ± 0.1% from 0 to 500°C is possible. This method does not necessarily work for sensors other than platinum. THERMOCOUPLE WIRES Resistance thermometers are widely SPLICED TO COPPER (COLD .IUNCl1051 used for the measurement and control of chemical, refinery, food and other man- FIG. 13-THERMOCOUPLE COLD JUNCTIONS must be kept at a constant temperature for correct ufacturing processes and in precision test- readings. Electronic temperature -compensation could also be used. ing of jet engines, large diesels, etc. Platinum offers the best precision of any conform to tables developed by TRANSDUCER MANUFACTURERS the Na- electronic temperature sensor, with sta- tional Bureau of Standards, and are cov- This list does not pretend to be complete. bility and repeatability better than by Each manufacturer ered specifications issued by the ± 0.1°C after use at 500°C (932°F) and listed makes a variety of transducers. American National Standards Institute beyond. They are available in most of the (ANSI). Other types of thermocouples are same assemblies shown in Fig. 12, but are Analog Devices in use and may be covered by future stan- generally enclosed in sheathed probes. PO Box 820 dards. Norwood, MA 02062 Thermocouples lack the sensitivity, ac- Thermocouples BLH Electronics curacy. and stability of resistance ther- A thermocouple is nothing more than 42 Fourth Ave. mometers or precision thermistors. They Waltham, MA 02254 two dissimilar wires joined together. It is are usable at much higher temperatures, based on the principle that if two different Boumes Instruments however, and are much more versatile metals are joined together, they will pro- 6135 Magnolia with generally lower cost. Types J,K, T duce an output voltage that is dependent Riverside, CA 92506 and E have sensitivities around 40 to 60 on the temperature of their junction. Over Celesco microvolts per °C while the platinum cou- the years, specific wire pairs have become 7800 Deering Avenue ples (R, S. and B) trade lower sensitivity standardized, with published voltage -vs. - PO Box 1457 (8 to 12 µV/°C) for higher temperature temperature tables and agreed -upon letter Canoga Park, CA 91304 use. Response is roughly linear. Standard designations. Types J. K, T, and E desig- Entran Devices accuracies are around ± 2.2°C or nate various combinations of chromel, 10 Washington Ave. ±0.75% of the temperature being mea- constantan, iron, alumel and copper. Fairfield, NJ 07006 sured. whichever is greater. Among them they cover the temperature Fenwall Electronics Thermocouples present a unique read- range from 200°C ( 328°F) to 1250°C - - 63 Fountain Street out problem in that their connection to (2282°F). Types R, S and B use combina- Framingham, MA 01701 copper circuitry creates additional cou- tions of platinum alloys to cover tempera- ples. Known as cold junctions. those con- tures up to 1800°C (3272°F). All seven Gould Inc., Measuring Systems 2230 Statham Blvd. nections produce additional voltages that Oxnard, CA 93030 vary with temperature. The actual readout will be the difference between the mea- Micro Switch CONTROLLED sured temperature and that of the cold 11 W. Spring St. R VREF junctions. SOURCE Freeport, IL 61032 In the laboratory, the cold junctions © Schaevitz Engineering may be held in an ice bath as shown in Fig. 130 Union Ave. 13. Published thermocouple tables as- Pennsauken, NJ 08110 sume that the cold junction temperature is

VOUT Sensym 0°C. In test or control systems that con- 1255 Reamwood Avenue tain many thermocouples, it is not un- Sunnyvale, CA 94089 common for all the cold junctions to be Weston Instruments placed in a constant -temperature heated Div. of Sangamo Weston, Inc. block. Most modern instruments, 614 Frelinghuysen Ave.Newark, NJ 07114 however, include "cold junction compen- FIG. 12-FOUR-WIRE MEASUREMENT elimi- Yellow Springs Instrument Co. sation" using a thermistor or semicon- nates errors due to lead resistances when mea- ductor sensor to automatically offset the suring with RTD's. A small amount of positive PO Box 279 feedback compensates for sensor nonlinearity Yellow Springs, OH 45387 cold junctions' voltages. when using platinum RTD's. continued on page 134

115 Upgrade Your Budget Printer

Many low-priced printers can be easily upgraded to give them new features and greater flexibility. Here's a look at some of the upgrade kits currently available for two of the most popular of those printers. HERB FRIEDMAN

elf you have been into personal computing from its Shack TRS-80 Model 1, the most popular computer of "hobbyist" days, or have built your system on a tight its day, hence the MX -80 featured a Radio Shack budget, it's odds-on that you have either an Epson graphics mode. Much of the modern software, MX -80 matrix printer or Smith -Corona TP -1 (or TP-2) however, is written for the graphics mode of the newer daisy printer. Either, or both, have probably given you MX -80 printers, which has the graphics capability for years of trouble -free service, but lately you find that the present most popular 8 -bit computers, the Apple ll more and more software can't be used with your and Ile. Even if the software is for other than Apple printer, or you want to upgrade the computer but find computers the graphics will most likely be intended for your printer can't quite hack it as an up-to-date printer the graphics capability of the most recent version of with the new computer hardware. the MX-80. Essentially, what you have is still functional The MX -80 (and its clones such as the Texas equipment that's been made obsolete by modern Instruments and IBM printers) accommodates only software, or by modern uses for a personal computer. tractor-feed paper. If you want to print on single sheets, The Epson MX -80 printer, which could be used with such as letterhead, the only way to do it is to use a any computer having a Centronics -compatible parallel special plastic tractor/pin feed "carrier," some of which printer output, was intended primarily for the Radio are prone to damage the printhead when pushed 116 EPSON'S OWN Graftrax-Plus upgrade consists of three ROM's supplied on a strip of conductive foam

THE PASSIVE TRACTOR FEED upgrade kit for the Smith - Corona printers. The main section is supplied as a complete assembly.

THE MICRO -GRIP single sheet upgrade kit. Its use does not interfere with tractor operation.

EPSON TELLS YOU to work on the printer with the cover attached, but don't do it-"pull the plug" instead.

THE FINGERPRINT module plugs directly into an Epson ROM socket. The existing ROM is moved to the empty socket on the board. through the printer mechanism. While the original MX -80 has a host of features such as compressed or enhanced printing it lacks a backspace, which precludes underscoring from some of the less expensive (but otherwise excellent) word processors THE THREE ROM sockets located in the base of the MX -80 that are available. printer. If you have an original MX -80 two of those are empty and one is filled. The "letter quality" Smith -Corona daisy printer TP family, which consists of the TP -1 and the newer TP -2, is the "buy of buys" when it comes to letter-quality can produce "camera ready" print quality the equal of printers for home -and -family and small businesses. The machines costing well over $1000 because it is TP -1 was the first under-$1000 daisy printer, which by essentially the printer end of a Smith -Corona electronic early 1984 was selling for as little as $250. Thousands typewriter with an accessory interface for computer upon thousands of personal computer users who output.) could not otherwise possibly afford a letter quality The problem with the TP -1 and the TP -2 is that they daisy printer struck gold in the TP-1/TP-2-the price were intended for single -sheet documents such as might very well be the reason you decided to get a business letters, etc., which is logica' because it is letter quality printer even though you already had a really the printer mechanism from a typewriter. But matrix printer. (If a type 251 ribbon is used-which was today, much modern software is intended for not mentioned in the early documentation-the TP -1 continuous forms printing, such as checks, labels, IRS

117 THE FINGERPRINT assembly snaps into ROM socket 1B, while the ROM that normally goes in that socket is installed on the Fingerprint assembly.

BEEPS FUNCTION t Reset 2 Compressed 3 Ooubie-wide 4 Emphasized 5 Double -strike Prev endow one 6 Perforation stopover second to hewn 7 Lett margin indent ekctien mode. 8 8 Lines/inch On'nee W NM» ruectron oetott 9 Banes tf r EM seNttlfn 10 Fine maot print

AN ADHESIVE MYLAR LABEL you affix to the front of the TO ADD the Micro -Grip single sheet feed to the MX -80 you printer lists the new functions provided by the Fingerprint. simply remove the collar securing the drive bar on the left side. schedules, even business stationary-which includes in the first place, user-installed retrofit kits are available letterheads and envelopes. To insure precise alignment that will upgrade either pnnter to accommodate of the printing, continuous forms must be tractor or pin modern needs. While some of the retrofits are better or fed. more convenient than othe's, we know those So what we have is a popular tractor-feed matrix discussed here will really work exactly as promised printer that needs at least new graphics capability and because we actually tried them out. the ability to feed single sheets, and a daisy printer that The first of the user-instal'ed MX -80 retrofits was needs a tractor feed in order to accommodate Epson's own Graftrax, which consisted of three ROM's, continuous forms. Let's see what we can do to satisfy two of which plugged into empty sockets in the base those important needs. of the printer while the third replaced an existing ROM. Among other things, the Graftrax upgrade provided for Upgrading the printers dot -addressable graphics, itallics printing, and even Regardless of why you purchased the MX -80 or TP -1 more important, backspacing. It was terrible

t r SLIDE THE ORIGINAL plastic paper guide roller from tie WHEN WORKING ON the Smith -Corona TP -1, you cannot driver bar and slide the two Micro-Grip rubber rollers on the separate the casing lop because the leads to the fan are too bar. Then replace the collar. short.

ATTACH THE PRESSURE roller EsserrbIy to tie paper bai IT APPEARS TO BE permanently installed, but the tractor and the single sheet retrofit is finished. mechanism goes on and off in seconds.

A SINGLE SHEET being printed by the MX -80 Be certain SUDE T-IE SUPPLIED GAUGE-actually a notched rod-on the pin -feed mechanisms are against the sides of the paper the drive bar, tighten two screws, and the tractor assembly it feeds straight. is adjusted for use. backspacing because the printhead returned to the true oackspace that puts graphic printouts in high gear extreme left and then advanced for each backspace, and relieves the strain on the printer's printhead-drive but it was adequate for general word processing: motor; a "4ine print' that can be used for superscripts underscore, kerning, etc. Unfortunately, a graphic and subscripts; automatic perforation skipover (no printout would cycle the head continuously until the more program listings printing on the perforations); and drive motor cou d be heard slowing to a crawl. a continuous underscore that. can be turned on and off The latest retrofit available from Epson dealers is from within a program or word processor. (A Graftrax-Pius, which gives your old model MX -80 the continuous underscore is formed simultaneously with advanced features of the latest model. Among the the character; the head does not backspace for the Graftrax-Plus highlights are the Apple -compatible underscore.) graphics (no more Radio Shack Model 1 graphics), a The Graftrax-Plus retrofit ki: consists of three ROM's

119 and the latest Epson-with-Graftrax printer manual- tuning" than printing. Just ignore the "fine tuning" which explains all the "bells and whistles." The instructions. Instead, gently slide the tractor pin -feed Graftrax-Plus retrofit has the same kind of installation as devices against the sides of the paper and apply their for the original Graftrax upgrade just plug the ROM's locks, thereby locking them in position against each into the correct sockets. One "caveat" however: The side of the paper. The pin feed assemblies will guide Epson instructions leave the top of the printer attached the paper so it rolls through nice and straight. The when you open the printer by separating the top and adjustment of the pin -feed mechanisms are bottom; it has you delicately balancing the cover on its "permanent" as long as you keep using single sheets. To end. If you look closely you'll see the wires to the use continuous form tractor paper you simply slide the switches in the cover are attached through a connector. two rubber rollers to the side and reset the tractors, or Mark the orientation of the connector with a pencil or leave the rollers where they are and pull the paper bail pen and then separate the connector and put the (with its roller) away from the paper; the Epson will cover in a safe place until you're finished. print on continuous tractor feed forms just as well without the bail. Pushbutton control Installing a tractor feed As long as you have the printer open consider a retrofit called Fingerprint (Dresselhaus Computer The tractor feed upgrade for the Smith -Corona Products, 837 E. Alosta Ave., Glendora, CA 91740), TP-1/TP-2 isn't really a retrofit because it does not really which allows the three printer control pushbuttons to become a permanent part of the printer, it can be also program ten operating modes: compressed print; easily removed in seconds. The tractor feed double -wide; emphasized; double -strike; perforation mechanism, which is available from some (not all) skipover; left margin indent; 8 lines/inch spacing; Smith -Corona dealers and the Smith -Corona service itallics, and fine print. For example, just touch the centers is a "passive" tractor feed, meaning it's really a printer's ON-LINE button twice and the printer shifts to guide that insures precise registration even though the compressed type without any commands from the paper is really driven by the normal platten computer. mechanism just like a single sheet. Fingerprint is supplied on a small printed -circuit While installing the tractor feed upgrade can be a board that swaps for the ROM in a socket 1B, the one user-performed task, Smith -Corona does not provide that's replaced in the Graftrax retrofit. Instead of the first three pages of the documentation with the kit; substituting for the ROM in socket 1B, install the Graftrax the pages that show how to do it yourself. Smith - ROM in the Fingerprint socket and then snap the Corona service centers will do the installation for $10 if Fingerprint assembly into socket 1B. You clip two you deliver the printer to the center. attached Fingerprint leads where indicated and you What's missing are these instructions. First, remove now have both the Graftrax and the Fingerprint retrofits, the casing top by loosening two screws at the top and with virtually no extra effort required on your part. front and then prying the top out of the three clamps in the base, thereby separating the casing top from the Single sheets base. The three clamps are across the rear of the base; If you quit now you'll have one heck of a matrix you'll need to use a large screwdriver as a pry bar and printer, but you can go one step farther and add a real you'll swear you're breaking the case but that's what it single -sheet feed by installing a Micro -Grip Friction takes to release the three clamps at the back of the Feed (Bill Cole Enterprises, Box 609, Wollaston, MA casing. Don't disconnect any wires even though they 02170). The Micro -Grip retrofit does not interfere with are short; just flip the cover up. the tractor operation, but it does permit single sheets Use common sense and remove the combination to be fed directly through the printer without the need dust cover and paper rest, and install the supplied for a plastic carrier. black metal strip (which is called an "electronics The Micro -Grip kit consists of three components: cover") so it spans the two screws that originally held two rubber rollers that replace the existing Epson the paper rest's pivots-remove the rest with its pivots. paper guide roller (which is sandwiched between the Remove the hinge -screws that hold the paper rest to two tractor pin feed mechanisms), and a rubber-roller the casing top. Drive out the hinge pins into which the pressure assembly that clamps to printer's paper bail- screws fit and gently drive in the new, supplied, hinge the bar that holds the paper down for printing. pins with a small soft -face hammer-or the back end To install the Micro -Grip retrofit it is necessary to very of a screwdriver. That's it-reassemble the cabinet. slightly dismantle the printer's feed mechanism so the The supplied documentation shows how to install rubber rollers can be fitted to the tractor -drive bar and adjust the tractor mechanism itself, all of a 10 (instructions are provided in the kit). It is, however, a minute job at the very worst. A special gauge is minor disassembly, and the whole installation shouldn't provided in the kit for alignment of the tractor take more than 10 or 15 minutes. Just be certain you mechanism. The whole project looks much more don't push or bend anything while you are doing the difficult than it is. Actually, separating the back of the work-do everything very, very gently. casing top from the base will be the most difficult part When you see the Micro -Grip installed you won't of the upgrade. believe it will work, but it does. The only problem is With the tractor-mechanism upgrade the TP-1/TP-2 the paper tends to skew, and the instructions on how can accommodate either single sheets, tractor-fed to "fine tune" the paper feed really don't do much of sheets, or tractor-fed forms and labels. As with the anything. You'll spend more time fussing with the "fine Epson retrofits, you lose nothing; you only gain. 4a*

120 C7

THE LOGIC ANALYZER CAN BEST BE LA1020 allows you to monitor and store The logic analyzer is a not- thought of as the digital equivalent to the 250 16 -bit TTL-level data samples. In a (analog) oscilloscope. However, unlike too -well -understood test typical microprocessor system, you the oscilloscope-which displays events instrument. We'll try to make would monitor the address, data, and con- as they happen-the logic analyzer sam- trol buses. ples digital signals and stores them as you more familiar with it by To hook the analyzer up to the system logic -level l's and 0's so they can be re- taking an in-depth look at one. under test, two data pods, like the one viewed later. Because of that fundamental shown in Fig. 1, are used. Each data pod difference, the operation of a logic ana- or probe samples eight TTL-level data lyzer may, at first glance, appear intim- lines, one QUALIFIER line, and one CLOCK idating. KENNETH PIGGOT line. The QUALIFIER and CLOCK lines will In order to dispel that feeling, we'll be explained in the "Triggering" section. discuss the basic operation of logic ana- Each data pod also contains the circuitry lyzers and take a close look at a relatively straight-line manner. Instead he may stop to terminate the sampling leads and to low-cost ($2075/$2475) unit: the model at the computer store, parts shop, etc. drive the connecting ribbon cable be- LA -1020/25 (manufactured by B&K Pre- In the real world we can observe the tween the data pod and the main unit. The cision 6460 W. Cortland, Chicago, IL path taken by the hobbyist simply by logic analyzer's MODE switch can be 60635). We'll also build a simple, single - looking at him. However, in the world of turned to the POD ACTIVITY position. IC logic analyzer. Although limited in its the microprocessor, our senses fail us and When in that position, each data pod acts capabilities, it can be used to demonstrate we must rely on instruments-like the as an 8 -bit logic probe with the display some of the logic -analyzer techniques logic analyzer that uses techniques such we'll describe. as address -state analysis-to see what is happening. Applications of logic analyzers When the address bus is monitored by a Although logic analyzers can be used B&K Precision logic analyzer during to monitor any logic circuit, they are each instruction -fetch cycle, 250 steps of mainly used on microprocessor -oriented the processor's program sequence will be circuits, usually to monitor the logic stored in its memory. By using various states of the address bus. That way, you trigger modes (we'll discuss those later), can follow the execution of the program you can begin the storage of program steps in a program. steps at any selected point of the pro- That's helpful because a program is gram's execution. rarely executed in a straight-line manner. The B&K Precision models LA1020 Instead, it will frequently branch off or and LA1025 logic analyzers feature many jump from one address to another at dif- of the capabilities of larger, more expen- ferent parts of the program. That action is sive machines. (The two models are iden- FIG.1-THE LP1 DATA ?OD or probe that is used analogous to a hobbyist on his way home tical except for the inclusion of signature - with the LA1020/25. Each pod monitors eight from work. He will not always travel in a analysis capability in the LA1025.) The bits of data, a qualifier line, and a clock line.

121 of the data samples occurs in conjunction 1 with the clock circuit. OPTIONAL The clock circuit tells the memory QUALIFIER QUALIFIER (16 BITS) when the incoming data samples are val- EXPANDER B&K LA1020 LOGIC ANALYZER OUTPUTS id. You can select between two external u clock lines (one located on each data pod) TRIGGER CIRCUITS I> EVENT or an internal clock. If you decide to use the external clock signals, either clock I nnA ENABLE line-and whether the rising or falling QUALIFIER (1 BIT) edge of the signal on that line is LOW used- DATA DATA (8 LINES) can be selected. It is important to note that POD the clock as it is referred to here is not SCO°E CLOCK (1 BIT) i necessarily the microprocessor system's DISPLAY MEMORY clock. It can be any control signal that's CIRCUITS ( used to indicate when the sampled data is -} SYNC valid. (1 BIT) QUALIFIER The appropriate control -bus signal for clocking the logic analyzer will vary with DATA (8 LINES) -> HIGH the type of data being observed and the DATA particular microprocessor in the system. POD i For example, if you wanted to look at the address lines of a Z80 microprocessor } EXTERNAL I INTERNAL "-CLOCK OUTPUT CLOCK I CLOCK during the instruction -fetch cycle, the CLOCK (1 BIT) -J clock line would be hooked to the READ L line and the clock edge would be set to inputs and outputs. FIG. 2-SIMPLIFIED BLOCK DIAGRAM if the LA1020 showing the external FALLING EDGE. Or, even better, a qualifier line would be connected to the MI line with the corresponding trigger switch set indicating 0's, l's, or P's (pulses), de- will be ignored. to logic 0. pending on the logic activity on each data An optional LP -3 qualifier pod (seen in When the internal clock is used, data line. Fig. 3) adds 16 more trigger bits to the will be stored at one of eight user -selected As can be seen in the block diagram in trigger word. With it, you could monitor a sampling rates ranging from 10 MHz (a Fig. 2, the two 8 -bit sets of data samples system's data lines while triggering from sample every 100 ns) to 1 Hz. That means from the data pods are routed to the logic the address lines that are connected to the it can take a minimum of 24.9 microsec- analyzer's memory and trigger circuits. qualifier pod. Sixteen three -position onds or a maximum of 249 seconds to fill As previously mentioned, the LA1020 can switches on the qualifier pod can also be the logic analyzer's memory. store up to 250 16 -bit samples in its inter- set to a logic 0, 1, or a "don't care" The internal clock allows you to ob- nal memory. Data sampling can occur at position. That optional expander pod is serve a circuit that has no clock signal sample rates of up to 20 MHz. (That plugged into a connector on the rear panel available. You could set the logic analyzer equates to a minimum time between sam- of the logic analyzer. to begin storing samples when a particular ples of 50 nanoseconds.) The easiest way to picture the operation set of inputs occurs and then store of the trigger circuit is as a multi -input periodic samples over the user-selected Triggering AND gate for which the active levels can be period of time. (See Fig. 4.) The trigger circuit of the logic analyzer user-defined by setting the TRIGGER BITS lets you select the starting point for stor- switches. When the logic levels on the 16 ing data samples. It continuously com- DATA lines and the QUALIFIER lines being pares the incoming data bits to a user- sampled match those set on the TRIGGER DO D1 BIT selected trigger word. That trigger word is switches, the memory -storage process 02 selected by throwing each of the 16 three - will be enabled. position TRIGGER BITS switches on the Before the various trigger modes are front panel to either i.o, or x, where the x described, it would be appropriate to ex- D3 0

stands for "don't care." In the "don't amine how the 250 samples are loaded D4 0 care" position, the incoming data line into memory. FIG. 4-A TTL CIRCUIT THAT can be monitored will satisfy the trigger requirements by a logic analyzer. The TRIGGER -BIT switches whether it is a logic 1 or a logic 0. would be set for the desired logic levels for The LAI020 also monitors a QUALIFIER DO D4. and for x for 05 D15. The internal - line from each of the data pods. That bit is clock selector is used to set the sampling rate. not stored in memory and is only used by the trigger circuit. Each of the qualifier bits has a corresponding switch that oper- Data storage ates identically to the TRIGGER BITS Once the trigger word and the clock switches. The easiest way to describe the source have been selected, the machine is purpose of the qualifier lines is to give an simple to use. You simply push the ARM example of how they could be used. If you FIG. 3-THE LP3 TRIGGER EXPANDER PROBE button to activate the trigger circuit. hooked one of the qualifier lines to a con- or qualifier pod adds 16 more trigger bits to the When the data on the incoming lines Lr) trigger word. co trol signal such as a microprocessor's match the trigger word, the analyzer will rn READ line, data storage would be trig- begin storing samples in conjunction with á gered only when the READ pin was high the selected clock. During the data -stor- zD (or low, depending on how the qualifier Clocking ing process, the TRIGGER LED will light. z switch was set). If the two qualifier lines Once the trigger circuit enables the When all 250 samples have been stored, w are not used, their trigger switches can be storing of data samples, it no longer has the TRIGGER LED will go out and the o set to the "don't care" position and they any effect on sample loading-the storing COMPLETED LED will light.

122 Let's consider, however, the real -life situation where the incoming data never QUALIFIERS QUALIFIERS matches with the trigger word. That typ- DATA DATA SAMPLES SAMPLES ically occurs when a up in program locks (16 BITS) LOGIC (16 BITS) LOGIC a loop. You can manually initiate storage ANALYZER ANALYZER the TRIG- MEMORY MEMORY of data samples by pushing the LOCATION LOCATION GER button. In that instance, if you are SAMPLE 11TRIGGER WORD SAMPLE 1 0 o sampling the address lines, the data stored +CLOCK DELAY) (TRIGGER WORD) will be the locations of the program in- SAMPLE 2 1 SAMPLE 2 1 CLOCK SAMPLE 3 2 SAMPLE 3 z structions then being executed. Also, if CLOCK you were to encounter an instance where a program halted before 250 samples were t I w stored, you could manually complete the SAMPLE 249 248 SAMPLE 249 248

sampling process by pushing the COM- SAMPLE 250 249 SAMPLE 250 249 PLETE button. Once the sampling process a b is complete, you can view the analyzer's stored data. QUALIFIERS DATA Data display DATA SAMPLES SAMPLES BITS) The display circuit shown on the block (16 LOGIC (16 BITS) LOGIC ANALYZER diagram in Fig. 2 lets you observe the ANALYZER MEMORY MEMORY stored samples. The LA1020 will display LOCATION LOCATION its stored information one word at a time SAMPLE 1 SAMPLE 1 -20 (TRIGGER WORD) 0 on its LED display when in the DISPLAY SAMPLE 2 -19 mode. By pushing the TRIGGER 1 + and - CLOCK CLOCK i 2 switches you can examine, individually, SAMPLE 20 each of the 250 data samples stored in the SAMPLE 21 (TRIGGER WORD) LA1020's memory. You can select your 1 SAMPLE 22 +1 choice of displaying the memory in a dec- 248 imal, octal, binary, or hex format by turn- 249 SAMPLE 249 +228 ing the MODE switch to the appropriate position. In addition to the data being FIG. 6-TRIGGER MODES OF THE LA1025. The basic mode is shown in a; the event -delay mode in b; displayed, the location of the data word in the clock -delay mode in c, and the trigger -position mode in d. the logic analyzer's memory is also displayed. The display circuit also supplies the synchronizing and vertical -input signals to allow an oscilloscope to be used as When the logic analyzer's MODE switch is position, the actual data stored in the cor- a 16-word by 16 -sample display. The data changed to the EVENT position, the logic responding bit position may be either a displayed on the oscilloscope will scroll analyzer acts as a digital trigger for an logic 1 or 0). as you scroll through the logic analyzer's oscilloscope. Whenever the incoming The basic trigger scheme can be altered memory. data sample matches the trigger word as when the MODE switch is turned to the There are two additional outputs on the selected on the TRIGGER BIT switches, a STAT (status) position. In that position, logic -analyzer unit. One is a CLOCK out- pulse that can be used to trigger an os- you can select any combination of event - put. When you select an internal clock cilloscope will be generated on the EVENT delay, clock -delay, or trigger -position rate, an output at the same rate is available output line. modification. from a BNC connector on the rear panel. A typical application would be to trou- Figure 6-b shows the effect of the event The other output is the EVENT output. bleshoot the analog input of an erratic A/ delay, which can probably best be thought D converter. By hooking the data -sam- of as a loop delay and can be used in the pling lines to the address lines and setting following way: Let's assume that you want the trigger bits to the starting address of to look at a program with a 300 -step loop SYSTEM UNDER TESTI the A/D conversion routine, as shown in that is going astray in its tenth pass DIGITAL Fig. 5, the oscilloscope can monitor the through the loop. In the basic triggering OUTPUT ANALOG INPUT stability of the input voltage to the A/D mode shown in Fig. 6-a, the logic ana- converter. lyzer would trigger and fill its 250 -word Id A/D CONVERTER OSCILLOSCOPE memory on the first pass through the loop. Trigger modes Using the event delay you can trigger the The real versatility of the logic analyzer logic analyzer on the tenth pass through START I ADDRESS lies in its triggering modes. We have al- the loop. To accomplish that, the MODE BUS CONVERSION ready discussed the basic trigger mode- switch is set to the STAT position and, for the configuration when the logic analyzer the example above, the event delay is set DECODING is powered up. As shown in Fig. 6-a, the to 9 by using the + and - EVENT DELAY I VERTICAL TRIGGER CIRCUIT I INPUT INPUT logic analyzer's trigger circuit monitors switches. By setting 9 as the event delay, the incoming 16 data sampling lines and you are instructing the logic analyzer to -_J qualifier bits. When the incoming data ignore the first 9 trigger-word matches samples match the user -selected 16 -bit (events) and to enable the logic analyzer's trigger word, a condition we'll call the memory when the tenth trigger event oc- LA1020/25 kENT trigger event occurs and the storage of curs. The event delay can be user selected OUTPUT data samples on subsequent clock signals to any number from 0 (no event delay) to FIG. 5-THE LOGIC ANALYZER can be used as a begins. In this mode, the first word stored 999. As with the basic triggering mode digital trigger for an oscilloscope. If the selected in trigger word is the starting address of the AID the logic analyzer's memory will be the (Fig. 5-a), the first data sample stored in conversion routine, the scope will be triggered trigger word. (If some of the trigger bit memory will be the sampled data that every time the conversion is started. switches are set to the x or "don't care" matches the triggering requirements. 123

The previous problem brings to light and the 124 samples after the trigger With an eight -bit data bus, eight ad- another problem. The loop length in our word, but also the 125 samples imme- dress lines (usually the lower eight bits) example above is 300 program steps and diately preceeding the trigger event. You can be stored in addition to the eight data our logic analyzer can only store 250 of can then see the data samples that oc- lines. The high -order address lines could those. Let's assume for this example that curred before the entry was made into the then be used as part of the trigger word by we want to see only the last 250 program subroutine. using the LP3 qualifier pod. Similarly, steps. To further complicate the problem, As previously mentioned, these three when monitoring a 16 -bit data bus, the the beginning of the program contains ten trigger modes can be combined for the address lines could only be used for trig- program steps that are followed by sub- desired effect. Although that task may gering. It is important to note that we are routine "A" (a ten -step subroutine). seem overly complicated to perform at confronted with the basic design limita- What's more, that subroutine is followed first glance, it really becomes easy after a tions of a 16 -bit machine-only 16 bits of by twenty-five program steps, a repeat of little experience. data can be stored at one time. Two alter- subroutine "A," and then by the re- natives are possible. One is to run two mainder of the program. An example LA1020/25 units in tandom. The other Note that since subroutine "A" ex- As another example, let us assume we would be to buy a unit with more than 16 though, a ecutes both from step 11 through step 20 are looking at a problem with multiple bits of data storage. Generally, and step 46 through step 55, we cannot set interrupt routines for the 8080, 8085, or unit with 16 bits of data storage is suffi- the trigger word to an address in sub- Z80 (mode 0). As there are 8 levels of cient for most requirements. routine "A" to capture the last 250 steps interrupts possible, the program could go A single -IC analyzer in our loop. That's because subroutine to any one of eight locations, depending "A" also occurs before the loop's pro- on the application. These locations are So far we have explored a commer- gram -step 50. shown in Table 1. cially available logic analyzer. Unfor- Keep in mind that we have already used In order to see which interrupt routine tunately, not everyone can afford more our loop delay to trigger on the tenth pass occurs, the address bus would be than $2000 for such a logic analyzer. Re- through our loop. The LA1020/25, monitored by the logic analyzer and the cently, I found myself in the same situa- however, has a trigger mode that allows trigger bits would be set to 0000 0000 tion. The B&K unit that had been loaned you to delay the storage of data samples OOXX X000 (binary A15 -A0) where X to me wasn't available any longer and I by a preset clock delay. That is shown in represents a "don't care" state. That didn't have the money to spend for one. Fig. 6-c. For our example above, you means that the logic analyzer will trigger Yet, the project I was working on-a would set the TRIGGER BIT switches to the any time an interrupt occurs. By modify- stand-alone printer interface card with an beginning address of our loop and set the ing the trigger position, you can see not on -board Z80 microprocessor-was giv- clock delay to 50 by using the + and - only what interrupt occurs but the address ing me a rough time. The program just CLOCK DELAY switches. The result is that of the program steps occurring before the wasn't executing as it should. Fortunately, after the event delay (Fig. 6-b) is satisfied a circuit that I had recently run across, was (it has priority over the clock delay), the adaptable to my needs. Based on that cir- unit will not store any samples until the TABLE 1 cuit, I was able to design a one -IC "logic clock pulse occurs. The remaining analyzer" to perform the function of ad- 51st Interrupt Subroutine loaded on subse- dress -state analysis. samples will then be level starting address (hex) quent clock pulses. In that manner, the Obviously, a one -IC logic analyzer will clock -delay feature gives you another tool 0 0000 have many limitations. The first limitation 1 0008 "zeroing in" on the portion of the with ours is that it will only work on Z80 for 2 0010 The microprocessors. The second limitation is program that you want to observe. 3 0018 that the output from the circuit under test clock delay can be set for values from 0 4 0020 2 on a host (no clock delay) to a maximum of 999. 5 0028 has to be fed into parallel ports The last triggering modification to be 6 0030 computer. discussed is the trigger position (Fig. 6- 7 0038 Figure 7 shows the typical hookup be- d). With the + and - TRIGGER POSITION tween the circuit under test and the host switch, you can locate the trigger event computer for address -state analysis. Fig- anywhere within its 250 word memory. If, interrupt. If the interrupt routine were a ure 8 shows an alternative method of dis- for example, 20 was set into the TRIGGER long one, the clock -delay function could playing the data if you don't have 2 extra POSITION register and the trigger event position the start of the sampling process parallel ports. occurs, 20 samples prior to the trigger anywhere within the interrupt routine. How it event will be stored in the first 20 words of works the logic analyzer's memory. The trigger Extended bus monitoring The circuit (its schematic is shown in word will be stored in the 21st position in In the case of monitoring a system with Fig. 9) is really quite simple. It causes the the logic analyzer's memory and then 229 extended addressing (more than 16 bits), microprocessor under test to enter a wait samples will be stored after the trigger the LP3 qualifier probe (Fig. 3) is useful. state at the beginning of every instruction - word. Even though the logic analyzer will only fetch cycle. While the microprocessor is This example, of course, assumes that store 16 bits at one time, the extended in its wait state, the address lines are the clock delay was not set. The trigger- address bits can be used to trigger the unit sampled by the host computer. The host position feature is perhaps the most useful with the LP-3 qualifier pod. Then, by computer then clears the wait signal and on the logic analyzer. Let us look at an knowing the address location of the trig- the microprocessor completes the instruc- example where you have a program that ger word, the 16 stored bits would gener- tion cycle. contains a subroutine where the program ally be enough to follow the program When the next instruction fetch occurs, is locking up. The trigger word can be set sequence. the rrc signal again goes low and the for the starting address of the subroutine A similar situation occurs when whole cycle begins again. A limitation (found by manually triggering the unit) monitoring the data buses. Eight- and six- that you should be aware of is that, unlike and the trigger position set to 125. (The teen -bit data buses can be monitored the B&K logic analyzer, which samples trigger -position register can be set to any without problems. A trade-off must be the circuit in real time (without slowing number from 0 to 249.) Now, when the made, however, when you want to moni- down the program's execution), this cir- sampling process is completed, you will tor both the address and data bus; let's see cuit halts the program's execution after not only be able to view the trigger word what's involved. each program step. Therefore, it is possi- 124 the start of the wait state until the host WAIT STROBE takes its sample-for the address lines to settle for a stable sample. Nonetheless, it REFRESH, is strongly recommended that the length Z80 DA7A (8 -BITS) CLOCK M1, ONE -IC of the connections between the tested sys- SYSTEM H OST LOGIC tem and the host be UNDER TEST ANALYZER SYSTEM system kept as short as possible. ADDRESS BUS DATA (8 When the program in 2 (16 BITS) BITS) Table is entered, a "*" is printed as a prompt. You

can then press any number between 1 and 9 on the keyboard. That pro- FIG 7- -INTERCONNECTION BETWEEN the logic analyzer hcst system and the test system. number of gram -step addresses will be displayed on ble that this circuit could cause some H OST -SYSTEM strange occurences in programs that have +5V CONNECTIONS TO CONNECTIONS A Z80 SYSTEM critical timing loops. UNDER TEST 4 The heart of the circuit is a simple dual PIN NO. FUNCTION 21 PR 7 D -type flip-flop. When the Z80's instruc- O GND 29-GND tion -fetch cycle begins and the ñil line IC1-a goes low, the next clock pulse toggles the STROBE C 1/2 74LS74 flip-flop, and the WAIT line is pulled low 6 via Q1. That transistor functionally acts as L 0 an open -collector output. Pin 24, the < 28 -REFRESH +5V WAIT line on the Z80, should be connected SI R1 24 -WAIT to a pull-up resistor. To protect any other 101- 1.2K 210 PR 01 non -open -collector gates hooked up to the 9 1/4W 0 2N3904 WAIT line, they should be disconnected. R2 1K Since a wait state occurs each instruction C 1/4W cycle when using this logic analyzer, that V +5V shouldn't cause too many difficulties. CL When a positive -going strobe is sent from Cl -b the host system, the second flip-flop is 1/2 741S74 toggled and the wait state ends. The Izs < 6 -CLOCK FRESH line prevents the wait cycle from INPUT DATA PORT < 27-M1 repeating until it goes high during the next BIT 0 <30 -AO

BIT 1 <31 -A1 BIT 2 <32 -A2 TO HOST -SYSTEM STROBE BIT 3 <33-A3 BIT 4 <34-A4 BIT 5 S2 <35-A5 BIT 6 <36-A6 BIT 7 <37-A7 BIT 8 <38-A8 BIT 9 <39A9 BIT 10 <40-A10 BIT 11 DATA BITS < 1 -Ali FROM LOGIC BIT 12 DISPLAY < 2-Al2 ANALYZER LED's BIT 13 < 3-A13 0 BIT 14 < 4-A14 BIT 15 t < 5-A15 GND <29-GND 2 FUG. 9-SCHEMATIC OF THE LOGIC ANALYZER. No on -board buffering is provided because enough lime for the data to settle is provided in software. When S1 is closed, the analyzer controls the test 3 system. When open, it has no effect on the test system.

BCD -TO -SEVEN - SEGMENT DECODER/DRIVERS b perf board using wire wrap techniques FIG. 8-AN ALTERNATE METHOD to display and is shown in Fig. 10. The connection to data from the one -IC logic analyzer. The circuit the host system was made by a 25 -conin a will cause an additional data sample to be taken each time S2 is pressed. Three additional ductor ribbon cable with DB -25 con- BCD -to -decimal decoder/drivers and LED's are nectors at each end. Connection to the needed to display the value of the 16 data bits. system under test was accomplished by using a 40 -pin clip with standard DIP spacing that attached to the Z80. No buff- instruction cycle. At the end of this article ering was used on the address lines be- FIG.10-THE ONE -IC we'll explore some options to expand the tween the system under test and the host LOGIC ANALYZER doesn't capabilities look elegant, but it does work! It was built using of this circuit. system. The software (Table 2) that I used wire -wrap techniques. Connection to the Z80 The circuit was built on a small piece of leaves a long enough delay time-from test system is by a 40 -pin clip.

125 TABLE 2-LISTING

This is a simple program to display the addresses of instructions as they are executed. When run, the program displays an "=r". The user then selects a number between 1-9 on the keyboard. That number of program steps will then be displayed on the console. If the RETURN key is hit, the system reboots. This program is written in 8080 code for the ASM assembler.

ORG 100H ;SETTLE :GET UPPER 8 DATA BDOS EQU 5 ,BDOS ENTRY POINT IN 05H ; BITS CONOUT EQU 2 ;CONSOLE OUT PRTHX ;PRINT HEX NUMBER : FUNCTION CODE CALL IN 06H ;GET LOWER 8 DATA CONIN EQU 1 ;CONSOLE IN FUNCTION CODE ; BITS ;PRINT HEX NUMBER 1XI SP,200H ;LOAD NEW STACK CALL PRTHX MVI E,20H ;OUTPUT A SPACE ON ; POINTER PMT: MVI E,ODH ;PRINT LINE FEED & ; THE CONSOLE MVI C,CONOUT ; CARRAGE RETURN MVI C,CONOUT CALL BDOS COUNT CALL BDOS POP D ;GET LOOP MVI E.OAH ; BACK MVI C,CONOUT DCR D ;DECREMENT LOOP CALL BDOS ;COUNT OUTPUT MVI E,2AH ;PRINT PROMPT JNZ LOOP ;LOOP UNTIL MVI C,CONOUT ; IS DONE CALL BDOS JMP PMT ;DONE - PROMPT ;USER MY SYSTEM I PORTS ARE: STROBE OUT PORT 03H SETTLING DELAY - ALLOW DATA LINES TO SETTLE STROBE OUT BIT =- 02H :LOAD DELAY LOW ADDRESS INPUT PORT = 06H DELAY: MVI C,10 COUNT HIGH ADDRESS INPUT PORT = 05H TLOOP: DCR C ;DECREMENT DELAY IS PORTS AND BITS SHOULD BE CHANGED JNZ TLOOP ;LOOP UNTIL TO REFLECT YOUR SYSTEM ; OVER RET ;DONE - RETURN MVI C,CONIN ;GET THE NUMBER OF

; HEX NUMBERS ON CONSOLE ; STEPS PRINT TWO CALL BDOS REGISTER CPI ODH :COMPARE TO PRTHX: PUSH PSW ;SAVE ASCII ;OUTPUT ONE ; CARRAGE RETURN CALL CHARACTER JZ O ;YES- THEN JUMP TO CPM POP PSW :GET CHARACTER CPI 20H ;CHECK FOR SPACE ; BACK ;BAR JMP BYPASS ;SKIP ROTATION ;POSITION DIGIT JNZ INC :YES -THEN ENTER 1 ASCII; RLC MVI A,31H ;ENTER 1 RLC INC: ORA A ;CLEAR CARRY FLAG RLC SBI 30H ;MAKE ZERO RELATIVE RLC FOUR MOV D,A ;PUT RESULT IN D BYPASS: ANI OFH ;MASK HIGH REGISTER ; BITS TO ZERO FOR HEX A -F PUSH D ;SAVE IT CPI 0AH ;CHECK THEN SKIP MVI E,20H ;OUTPUT A SPACE ON JC PASS ;NOT ; NEXT ; THE CONSOLE TO MVI C,CONOUT ADI 7 ;INDEX "A" TO ASCII CALL BDOS PASS: ADI 30H :INDEX OUTPUT POP D :GET COUNT BACK MOV E,A ;POSITION ;OUTPUT IT LOOP: PUSH D ;SAVE LOOP COUNT MVI C,CONOUT MVI A,2 ;OUTPUT STROBE CALL BDOS OUT 03H RET END f CALL DELAY ;ALLOW SIGNALS TO

should be used to insure the terminal's CRT. In that way, the execu- the Z80, the requirement for the refresh circuit. Caution any restrictions on the maximum du- tion of the program can be followed. signal can be eliminated by adding an that wait signal should not be When you want to exit the program, sim- inverting gate from a 74LS00 or 74LS04. ration of the (The Z80 has no restriction on ply press the carriage return. The input of that gate would be connected exceeded. duration of the wait signal). It's possible that you would like to see from pin 12 of the 74LS74 and the output the maximum I its limitations, this simple log- all memory accesses by the Z80 in addi- of the gate would be connected to pin of Despite the requirement ic analyzer enabled me to successfully Lo to the instruction fetches. The memo - the 74LS74, eliminating co and saved me the ry-request signal (Z80 pin 19-MREQ) and for the resetting of the logic analyzer via complete my project I cost of an expensive logic analyzer. With the READ and WRITE signals (pins 21 & 22) the Z80 refresh signal. Although haven't a little work with the software, many of D are candidates for triggering signals that actually tried it, the address latch enable or the valid memory the features of the commercial logic ana- z could be used in place of the n%II signal to (ALE) of the 8085 could be a trigger the unit. address (vMA) of the 6800 should take the lyzer we previously discussed R -E If you use a microprocessor other than place of the iTt signal in triggering this implemented. 126 maximum open -circuit EQUIPMENT REPORTS voltage is less than by depressing the RANGE SELECT button. .4 volt in the LPsa mode.) When you do that, the AUTO annunciator continued from page 20 Another good way to get an idea of the will disappear from the display. As you capabilities of the 3500 is to take a look at step through the ranges, the decimal point the face of the unit and its controls. A 10 - In fact, the company discourages any user on the display will change, as will the unit mm, 31/2 -digit LCD readout dominates adjustments by stating that such un- annunciator. the top half the unit, while a large rotary authorized adjustments will invalidate the One advantage of using the manual switch (which lets you choose voltage, range unit's one-year warranty. One bit of useful mode is that the meter's response resistance, or one of three current ranges) is information that is provided time improved for some measurements. is a list of dominates the bottom national frequency allocations. The half. Three push - For example, while the response time push switches are located beneath the dis- when making resistance model Z30 sells for $269.95. R -E or AC voltage play. The first lets you choose AC or DC measurements is 5 seconds (maximum) in modes (when measuring voltage or cur- the autorange mode, it is only 3 seconds rent) or normal or low -power ohms (when (maximum) in the manual mode. The re- Triplett Model 3500 measuring resistance). The second but- sponse time for DC voltage measurements Autorange Digital ton, RANGE SELECT, lets you choose the is the same in either the auto or manual Multimeter proper resistance or voltage range. (When modes, about 3 seconds maximum. The first turned to the VOLT or OHM mode, the maximum response time for current mea- unit is in its auto mode until the RANGE surements is about 3 seconds for DC and 5 A "user friendly" hand-held SELECT button is pressed. The current seconds for AC current. (Remember, au- multimeter for the hobbyist ranges are chosen only with the rotary torange capability is not available for cur- or switch.) The third professional button, ZERO ADJUST, rent measurements.) is used to zero the resistance reading when A useful "extra" feature of the 3500 is the leads are shorted together. It can also be used in the voltage or current modes to Triplett 3500 make offset measurements (as long as the OVERALL two least -significant digits are less than PRICE 19). EASE Three input jacks are centered at the OF USE bottom of the unit. The only time the leads INSTRUCTION have to be changed is when making cur- MANUAL rent measurements in the 10 -amp mode. PRICE All of the jacks are of the recessed. VALUE The accuracy specifications of the 3500 1 2 3 4 5 6 7 8 910 should suit the professional as well as the hobbyist. When measuring DC voltage, your measurements will be, at worst. accurate within to .75% of the reading ± I its audible tone. In the voltage or curren digit (when the meter is correctly cali- modes the tone is used (along with a brated). For AC voltage measurements, blinking initial "1" in the display) to indi- CIRCLE 246 ON FREE INFORMATION CARD the worst -case specification is 1% of the cate that the tester is overranged. In the reading, 3 ± digits (for signals between resistance mode, the tone is used for a 01. ALL THE DIFFERENT TYPES OF ELEC- 40 and 500 Hz). In either resistance mode, continuity indicator-it will sound when tronics test equipment available, the in- you can expect your measurements to be the two least -significant digits are less strument that's bought more than any accurate within 1.5%, ± 1 digit. The ac- than 19 (in any range). Those of you who other is the multimeter. The handheld dig- curacy of the 3500 drops when measuring find those tones annoying will be happy to ital multimeter seems to be the type fa- current: 1.7% ± 1 digit DC, 1.7% ± 3 know that the feature can be turned off. vored by most buyers today. We recently digits AC. had the opportunity to examine a good If you plan to make in -circuit measure- Protection representative of that class of instruments with your multimeter, there are No matter how careful you are, it's all ments-the model 3500 from Triplett some additional specifications that you too easy to put excessive voltage across Corporation (One Triplett Drive, should look at. One of those is the input the meter probes. For example (although Bluffton, Ohio 45817). impedance, which is at least 10 megohms no-one likes to admit it), almost everyone Although the 3500 is an autorange on all voltage ranges. When making cur- has at one time or another tried to measure model, its measurement ranges can be rent measurements, the voltage drop a voltage with a multimeter that was in its selected manually. Let's take a look at across the instrument is, at worst, 2/10 resistance mode. That is, of course, why those ranges-it's perhaps the best way to volt. For in -circuit resistance measure- manufacturers design protection circuits get an idea of what the 3500 can do. Its ments, the open -circuit voltage drop into their meters. For voltage measure- voltage ranges are: 2, 20, 0.2, 200, and across the leads is important. That voltage ments, the 3500 is protected up to 1000 - 1000 volts DC and 2, 20, 200, and 600 is less than .4 volt in the low -power-ohms volts DC and 600 -volts AC. In the resis- volts AC. Its DC and AC current ranges mode, and less than 1.5 volts in the high - tance and current modes, the unit is pro- are 20 mA, 200 mA, and 10 amps. And its power -ohms mode. tected up to 250 volts AC. As for other resistance ranges are 200, 2K, 20K, types of protection, its rugged plastic case User features 200K, and 2 megohms. A low -power- should protect it against rough handling. ohms measurement mode is also offered, The most "user-friendly" feature of the The 3500 requires 2 "AA" cells-you with ranges of 2K, 20K, 200K, and 2 3500 is its autorange capability. When can expect 300 hours of operation from megohms. In that mode, you can measure making voltage or resistance measure- two alkaline batteries. A low -battery in- in -circuit resistances that are shunted by a ments, there is no need to select a mea- dicator appears in the display when there silicon diode or other such junction device surement range. However, you can, as we are less than about 50 -hours of operating without turning on the junction. (The mentioned earlier, select ranges manually life remaining. turn page

127 I .5

ling capacitors at the AM decoder outputs a 470 -ohm resistor. The result with this AM STEREO took care of that low -frequency problem. receiver was excellent AM stereo, al- varac- though the lack of a front end RF amplifier continued from page 6 4 An RC filter on the DC line to the tors eliminated the 600 Hz tone. made reception of some stations difficult. That Sears radio worked out very well. Final suggestions played along with the band, mono -stereo Although it is not microphonic, it is sensi- mode and tape track. The IF is 262.5 kHz, tive to phase changes. Faint modulation In radios that are AC powered, it may and the bandswitching is all -electronic. from other stations can sometimes be be necessary to suppress noise caused by The section of the tuner that is not in use heard when the selected station is quiet or rectifier circuit diodes. If a sharp buzz is has its DC supply turned off Therefore a has very low modulation. That would heard, it may be the result of these power- single -transistor switch was added to ap- probably not be a problem in an auto- switching diodes. The problem can usu- propriately operate the AM-stereo de- mobile. Its bandwidth is much narrower ally be corrected by installing a .05 µF, coder -circuit. The entire AM -receiver than the Realistic portable which is no- 250 -volt (minimum) ceramic disc capaci- in the power supply section is a single IC but, fortunately, its ticeable in the audio -frequency response. tor across each diode 1F output voltage is high enough. In fact, But it's still acceptable. especially for au- circuit. as lamp we had to decrease it by using a 4.7K tomotive use. Household devices such dim- resistor in series with the decoder input. The third conversion was installed in a mers or remote -control units that operate The decoder VCO circuit shown in Fig. IO home stereo receiver, a Technics model lights and appliances can generate tre- is by was used to match the 262.5 -kHz IF. The SA -722. This receiver has a fully syn- mendous noise, which distributed audio outputs were connected in parallel thesized control and tuning system that's the building's electrical wiring like a huge this with the outputs of the FM multiplex de- operated by a microprocessor. The syn- antenna. AM radios will pick up very coder. Since power is switched for band thesizer presented noise problems in the noise and make listening unpleasant man- selection, the connected audio outputs did very -low -frequency area and required a if not altogether impossible. The not interfere with each other. Series resis- minor modification to a filter in the preset ufacturers of these devices may be able to tors had to be inserted in the decoder's tuning circuit. offer methods or reducing the problem. audio outputs because their level was A small resistor was added to the loop - Otherwise, they will have to be turned off higher than that of the FM section of the antenna circuit to lower the Q of the loop. or disconnected when using the AM re- radio. Doing that kept the sound level That helped maintain a satisfactory band- ceiver. about the same when switching between pass over the entire AM band. The origi- Installation of an outdoor, long-wire antenna for the band may allevi- bands. Also, we made up a special PC nal detector circuit was also modified to broadcast board for the decoder so that we could fit it smooth AGC response and control. (The ate most of those interference problems. inside the tightly packed radio. detector circuit, although not used for Another, perhaps more important benefit The stereo system worked well, but the stereo reception, generates AGC voltages is that an outdoor antenna will provide a digital control -system caused phase -gen- and had to be kept intact.) That modifica- greater source of stereo signals. erated tones at about 600 Hz and also at tion could have been skipped, but a no- In the near future, when many major, about W Hz (fluttering). The tuner PLL ticeable improvement resulted in output music -program AM stations have intro- loop compensation frequency was sneak- from stations across the hand with widely duced C-QUAM stereo broadcast, you'll ing through the DC control lines to the varied signal strengths. no longer be limited to hearing good ster- varactor in the tuner section, causing Audio outputs were connected in paral- eo from local FM station whose range is phase modulation and some frequency lel with the outputs from the FM multi- limited roughly to line -of -sight. You'll be modulation that appeared loud and clear plex system. The stereo indicator already able to hear the AM stations from hun- in the audio. Rolling off the audio re- in the receiver could be driven directly dreds of miles away (as you can now, es- sponse below 50 Hz with smaller coup- from the AM decoder lamp drive through pecially at night), but in full stereo! R -E

EQUIPMENT REPORTS Beta Electronics Pro -Kit I PC -Board Fabrication Kit continued from page 127

The instruction manual that's supplied with the meter is adequate. It includes- Using a stencil is the best along with a listing of specifications and instructions-a parts list, schematic, and way to make a group of a parts -placement diagram. printed -circuit boards that The 3500 has a suggested price of $140, which is about what you'd expect to pay use the same circuit pattern. CIRCLE 247 ON FREE INFORMATION CARD for an instrument with similar specifications. It comes equipped with two test probes with screw -on alligator clips. MOST OF THE CONSTRUCTION PROJECTS 92057). The kit is best suited for making Other accessories are also available, in- presented in the pages of Radio Elec- more than one board at a time-once cluding a temperature probe, two high - tronics require the use of a printed -circuit you've done one board, it's not much makes voltage probes (6 kV and 30 kV), a 20 - board. Even when it's not mandatory, it's more work to do twenty more. That school amp external shunt, and a variety of carry- usually a good idea to use one-PC Pro -Kit I well suited for club or ing cases. You'll probably want to get one boards can reduce wiring errors and make projects that require many boards of the a same type. But because the results from of the cases-the 31/2 x 6 X 15/8 -inch unit is troubleshooting easier. But if prepared too large for a shirt pocket. board isn't available, what do you do? Pro -Kit I are close to professional quality, One solution might be to make your you could even use it in business applica- You'll find more Equipment Reports in own, using a PC -board fabrication kit tions. every issue of Radio -Electronics. Check such as Pro -Kit I from Beta Electronics Pro -Kit I uses a screening method (the 'em out! (2081-A 3rd Street, Riverside, CA same method that's used professionally):

128 you first make a stencil (pho- enough speed to print 75 or more of the 2 cups of developer at a time. tographically) of your PC -board layout same images in one setup. (If you let the and apply resist ink to a copper-clad board screen sit too long, the ink will dry on the What you get using the stencil-but it's not as easy as all screen. But even if that happens, and you Let's see what is contained in Pro -Kit !: that, as you'll see as we go through the still want to print the image more, you can a workboard and a screen (15 x 15 inches); process step by step. use lacquer thinner to clean off the ink a 12 x 12 -inch contact printer (a felt -cov- Once you have your artwork com- without disturbing the stencil.) ered wood base with a glass cover); photo - pleted, you'll need a right -reading emul- Another advantage of the screening stencil material (8 x 42 inches); a sion positive which is used to expose the method is that it can be used for things squeegee for ink pulls; a spreader for stencil material in the contact printer other than applying resist ink to copper- block -out; an 8 x 12 inch plastic tray for that's included with the kit. (The stencil clad boards. For example, you can (using developing and etching, stencil developer material can be exposed in direct sunlight, the appropriate ink) print component leg- (two packages of powder that are mixed or under a sun lamp.) After exposing the ends on PC boards, or the legends on the with water), two single -sided copper clad stencil material, you have to develop it, front panel of your next project, or use it to boards (4 x 12 and 6 x 12 inches), and two rinse it, and then place it on the screen. print the PC -board solder mask. And you double -sided copper -clad boards (4 x 12 can use it for non -electronics hobbies too. and 6 x 12 inches). Pro I Beta Electronics -Kit For example you can print posters or de- The instruction manual is 16 pages and OVERALL signs on fabric (but you'll probably need a is-as its introduction states-written PRICE vacuum -frame contact printer for best re- with the hobbyist in mind. The manual EASE sults). isn't perfect, but it's much better than OF USE Of course, there are some disadvan- most. It's amply illustrated and is laid out INSTRUCTION tages to this method as well. It can be very in a logical and organized manner. What MANUAL messy, and it takes quite a lot of practice is missing from the manual is a brief over- PRICE to get consistently good results. That's view of the process before the step-by-step VALUE why our rating chart shows only a "fair" instructions. If you're unfamiliar with 1 2 3 4 5 6 7 8 910 mark for "Ease of Use." Of course there's silk-screening, you'll have to read

< '<1. Gad cf no easy way to make PC boards-until through the manual a few times to get the you get the hang of things. The Pro -Kit idea of it. We did like to see the following takes a bit longer to learn than other meth- note at the beginning: "Practice makes After blotting up the excess water with ods, but it can do more as well. perfect...the more you use your kit, the newspaper, block -out is applied around Another disadvantage to the kit is that better your results will be." the stencil material. That, when dry, will you'll be working with some dangerous With Pro -Kit !, you can make near - prevent the resist ink from flowing chemicals. Of course that's true whenever professional -quality PC boards. It's not through the screen. (It helps to save ink you make a PC board, but there are more suited for the casual hobbyist, But if and keeps the work area cleaner.) of them in Pro -Kit I. The only chemicals you're a serious hobbyist, and make a lot When everything is dry (about 2 hours that don't have to be mixed are the resist of PC boards, then Pro -Kit I might be a later), you can pull off the stencil mate- ink and block -out. The etchant (am- good way to go-especially if you make a rial-but all that is removed is the plastic monium persulfate), ink stripper (tri - few boards of the same pattern. If you sheet-the emulsion stays on the screen in sodium phosphate), and developer (chem- don't make a lot of boards, then the the area where you want the copper re- ical name not given) must be mixed with $99.95 cost is probably too expensive. moved (and prevents the resist ink from water. Beta Electronics offers a copper- being applied to the copper). The com- The developer for the photostencil film plating and solder-plating service at $.05 bination of the block -out and emulsion on comes as two packages of powder which per square inch ($3 minimum). They will the screen makes up the stencil. must be mixed together with one gallon of also drill your board for $.04 per hole and Now that the stencil is all prepared, you distilled water. Unfortunately, you must can produce your photography ($5 for place your copper -clad board under the discard the solution at the end of the day. 5 x 7 inch artwork), and they can do the screen and then pour resist ink on the (If stored, it forms a powerful gas.) But complete fabrication of your PC board screen and "pull" it over the stencil. the manual gives instructions for making ($75 minimum). R -E When the resist dries, you can etch the board. All that's left to do is to clean up.

The advantage of screening Kaypro 10 Hard Disk You might wonder what the advantage Computer of the Pro -Kit method is. After all, you could have gotten the same results, with fewer steps by using a photo -resist method. But what if you wanted to make an- This portable computer comes other board? If you used a photo -resist complete with a hard disk and method, you'd have to expose another bundled software. board and worry about the exposure CIRCLE 248 ON FREE INFORMATION CARD times, rinsing, etc. And if you wanted to expose five more boards, you'd have to do the same thing five times more. With Pro - FOR JUST A FEW DOLLARS MORE THAN THE hard disk, a double -density two-sided Kit I, all you'd have to do is to place cost of adding a separate hard -disk unit to floppy -disk drive, and most of the soft- another copper-clad board under the an existing computer system, you can ware you'll ever need. screen and "pull" some more ink over have a full -featured portable computer it-you no longer have to worry about with hard -disk mass storage from Kaypro Description exposure times. Beta claims that, with Inc. (533 Stevens Ave., Solona Beach, Outwardly, the Kaypro 10 closely re- practice (a lot of practice, as far as we CA 92075). The computer system. priced sembles the well-known Kaypro II in could tell), you should be able to get at $2795, features a built-in 10 -megabyte overall size and appearance, though it's

129

vent knocks and from causing the slightly heavier at 31 lbs. The computer is Kaypro Kaypro 10 jolts housed in a metal cabinet with a carrying hard disk's heads from crashing into the handle on the top. When placed flat on a OVERALL disk and damaging the magnetic surface? PRICE table, two catches release the keyboard The very last thing the user does before panel of the com- EASE shutting down is to run the short and fast unit revealing the front OF USE puter. The typewriter-style keyboard con- SAFETY program that parks the heads on INSTRUCTION a safe area of the disk. With the heads tains four-way directional keys and a MANUAL separate 14-key calculator -style numeric parked, knocking the computer around PRICE causes no damage to the surface of the keypad. The front panel of the computer / VALUE hard disk. contains an 80 -column x 24 -row 9 -inch 1 2 3 4 5 6 7 8 910 Keep in mind that in the past Kaypro green monochrome anti -glare CRT dis- cpck has and changed play. To the right of the display there's a ems` E°t continuously upgraded the software bundled with their comput- power-indicator lamp, a hard -disk -ready ers, so that by the time you read this report lamp, and a vertically mounted half- height floppy -disk drive. the bundled software that is being A swing -out tilt bracket elevates the py disk, thereby freeing the hard disk for provided with the computer might be even be front of the computer so that its bottom is data storage. (As you can see from the completely different. There might level with the top of the keyboard. The tilt preceeding, the system is extremely flexi- several different packages. In that case, be- bracket allows easy access to the floppy - ble and easy to handle.) you might even be allowed to choose disk drive. It also positions the display tween different software packages at no extra cost. screen so that it's tilted directly toward the Software it one of the few com- The list of software provided by Kaypro user's eyes, making Instructions puter displays that won't give you a stiff at the time this report was prepared in- neck after extended use. Unfortunately, cluded: MBASIC, an easy-to -use BASIC We had the fourth draft of Kaypro's own most computer displays are too high, and language for the beginner and experi- preliminary operating manual for the you'll really appreciate having the tilt enced programer; SBASIC, an advanced computer. It was excellent: notably clear, bracket after several hours at the computer BASIC language that you can use to write well organized, with an excellent table of punching in data. your own programs. There's also Perfect contents (among the best operating man- In addition, the display is recessed so Writer (a word -processor program) and uals we have seen). Unfortunately, the that it's shielded from overhead lights and Perfect Speller (a spelling checker), The same cannot be said for the other soft- is the its face is etched to sharply reduce the Word Plus (a highly rated spelling check- ware, whose documentation origi- affects of room glare. The screen position er), and Perfect Filer (a database pro- nal from the software houses. Except for and antiglare precautions make that dis- gram). In addition there's Perfect Calc (a The Word Plus documentation, the replay one of the best we've seen for long- "What If...?" program), Profit Plan mainder of the software documentation term viewing. ("What If...?" business planning), and a was the usual wordy, dull, tutorial style Turning to the rear of the computer we game package. Also included are the usu- that has come to characterize personal - computer manuals. find a power-cord receptacle along with al CP/M utilities such as PIP and SUB- storage clips for the cord, the power MIT, as well as some unusual but The only real complaint with the com- switch, a reset switch, a brightness con- extremely convenient routines. For exam- puter is the female Centronics -type socket trol, and a parallel -printer output with a ple, one utility allows the user to in- connector used for the parallel printer out- Centronics -type connector. The rear panel stantaneously select the baud rate for the put; it's the wrong gender. A socket is also contains two standard RS -232 I/O modem RS -232 port, while another utility generally used on a printer. The computer ports-one that can be used for a serial allows the simultaneous selection of a dif- should have a plug connector so a stan- printer and the other for a modem-and a ferent baud rate for the second RS -232 dard extension or connecting cable can be modular telephone connector for an op- port. (Since two serial ports have been used. (And anyone who's ever looked tional light pen. In addition, there is an- provided, you, of course, can have both a knows, it's not easy to locate a male -to- other modular connector for the con- modem and a serial printer connected at male cable in local computer stores.) necting cable that is used to connect the the same time; the modem does not dis- Other than the printer connector there keyboard to the computer. able the printer.) are no complaints, not even nit-picking. The main features of the Kaypro 10 are SAFETY is the software that permits The Kaypro 10 does exactly what it's sup- the internal 10 -megabyte hard -disk, a the hard disk to be truly portable. As you posed to do-and it does it remarkably CP/M operating system, and an extensive might have wondered, how does one pre- well. bundle of software. (Bundle means software supplied with the computer at no additional cost.) The hard disk has a basic CRYSTAL TESTER capacity of 10 -megabytes and is automatically partitioned to function as drives A IF YOU FREQUENT HAMFESTS, ELECTRON- course, is to find some way to weed out the and B. Almost all the softwear is dupli- ics flea markets, or any other type of sur- obviously bad parts before you buy them. cated on drives A and B and is so exten- plus outlet, you know the pros and cons of The circuit I'll be describing here has sive that it uses more than 2.5 -megabytes buying from those sources. On the one proved useful for just that purpose when of storage, thus the hard disk comes with hand, they're an excellent source of hard - digging through stacks of crystals, as well almost 6 megabytes already in use. to -get parts as well as a haven for bargain as in troubleshooting my equipment. It is If the user inadvertently hunters. On the other, however, just about small, easy -to -build, and will, at a co "blows"(erases) a program on, say, drive everything is sold "as is," with no guar- glance, let you know if a particular crystal °' A; it can recopied on drive A from drive B antee of any kind-it's strictly "let the will oscillate. Let's look at the circuit Q using the PIP (copy) command. The flop - buyer beware." If you've ever come home shown in Fig. 1. z py-disk drive is used as drive C and with a pile of components, only to find out Transistor Ql, a 2N3563, and its asso- provides 390K of storage. That drive can that half of them were useless, you know ciated components form an oscillator cir- w be used to make back-up copies. Almost that not all bargains are what they seem. cuit that will oscillate if, and only if, a cc all the software can be transferred to flop- The ideal solution to that problem, of continued on page 134

130 1ii1r1 r¡': :.iG:si ! .LtC :I4! 15r%-36S P//}^vf'I Radio- 4lÑG.L IYÍLi EIecIron G atSw 4 test P:L1°'.tSI.S{K`á to, .kifiSid

Türi3fSÿ t c work/wide P Step-by-step TV Ke7,. COMPLETE ir ILpBLE COH fort e FIRST TIME.

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Send today for your 52 -page (81/2 x The robot is fully mobile with minipu- THE BODY-FRAME AND ROTA- 11") booklet containing complete re- lator arms to grasp, lift and carry. TION MECHANISM. This is the part prints of all eleven articles in the that makes Unicorn -1 look like a ro- Build Your Own Robot series by Jim MANIPULATOR ARMS and end - bot. Wood and Formica are the ma- Gupton. effectors (hands) are what enable the terials for the body. Motors and gears robot to perform useful tasks. Details are what make it function. of construction techniques and con- This all-inclusive reprint gives you all siderations are fully explored. the data you need to build your own COMMUNICATIONS. How you can Robot. tell your robot what to do. Prepro- MOBILITY is BASE not a lunar gramming techniques....radio control space station. It is the drive system ....computer control are all detailed. TELLS EVERYTHING YOU NEED that permits the robot to move from TO KNOW to build the Unicorn -1 here to there. Full construction de- Robot without the need for an engi- tails along with a discussion of power SENSORS. How to add sensors so neering degree or special equipment. sources is included. your robot doesn't bump into things.

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I want to order reprints @$12.00 plus $3.00 (Street address) Air Postage and handling for all other countries. U.S. Funds only. (City) (State) (Zip) Allow 6-8 weeks for delivery. We do not bill, check must be enclosed. HOME CONTROL COMPUTE resistor for the thermistor are all that is required. The software to drive that circuit CABLE DESCRAMBLING continued from page 93 is just as simple: continued from page 110 Both of those devices can be connected 700 OUT(16,1): REM A/D CHAN- directly to one of the A/D converter's in- NEL 1 put channels and the result can be scaled 710 OUT(32,0): REM START CON- to read degrees. But suppose you just VERSION reach into the junk box and come out with 720 LET B = INP(32): REM D/A 50 mV PP an unmarked, unknown thermistor. You OUTPUT VOLTAGE IS can connect it to the input of the A/D STORED IN B converter with a pull up resistor to 740 REM VARIABLE C CONTAINS + 5VDC. Using IF statements, your pro- DESIRED OUTPUT gram can find the correct temperature: 750 REM RC IS CONNECTED TO 100 OUT(16,0):REM CHANNEL 0 BIT ADDRESSABLE OUTPUT CONNECTED TO THER- 0 2.5 VI P -P MISTOR 770 IF BC OUT(0,0): REM DIS- 120 LET A = INP(32):REM ASSIGN CHARGE CAPACITOR RESULT TO A If you wanted to compute the average tem- 200 IF A = 0 PRINT "45" perature since the unit was turned on: 201 IF A =1 PRINT "44" 800 LET D =D + 1: REM THE 202 IF A = 2 PRINT "42" NUMBER OF SAMPLES 1.5 V P -P 810 LET E = E + A : REM THE AC- CUMULATED TEM- PERATURES 455 IF A = 255 PRINT "5.8" 820 LET F=E/D: REM THE AVER- 500 PRINT "DEGREES" AGE TEMPERATURE 510 GOTO 100 Although that program will make any pro- That illustrates the advantages of smart fessional programmer shudder, it works, control over a traditional thermistor/lin- 4.80 V P -P it's simple, and it doesn't require hours of earizer/meter approach. Although more One of the features that makes complex initially, the control computer is debugging. 63ms- this computer so powerful is that it can be unlimited in its adaptability. up -and -running in a minimum of develop- Of course, now that you have the tem- d ment time. perature information inside the computer, Now, suppose we wanted the output of you can use this data to control any of the to go to a DVM outputs. Those can control your home our digital thermometer 0.76 V P -P instead. The simple D/A plus the pull-up heating system etc. R -E

WHEN TESTING THE DECODER, look for the following signals: The Input should look something Ilke what's shown in a. The signal in b should be seen on pin 5 of IC1. The signals In c and d should be seen at the base and collector of 03 respectively. The waveform shown In e should be seen at the junction of RIO and R11.

nal to return the horizontal -blanking pulse (which contains the horizontal sync and C ' colorburst information) back into its prop- r ---,...j >x»rxt..,..t ºrrr arxrat er location. The scrambled video should ... re...... ; be clear. Once the circuit is working properly on one scrambled channel, you will have to switch to other scrambled channels to see if the circuit is tracking properly. If it isn't (and some channels are not being properly descrambled), some minor, final touch-up adjustments will have to be made. Remember that switch SI has to be open to view a scrambled channel, and must be closed to view a non -scrambled channel. Unless you modify the circuit with a bypass -switch arrangement, it will THE FINISHED PRODUCT. The hinged spacers at the rear of the board let you tilt the computer board be necessary to leave this circuit on when- up, giving you easy access to both boards, while keeping the size of the system down. ever you watch TV. R -E

132 HOW YOU AND THE COMPUTER This will be CAN BE FRIENDS .. to Getting Started coming you Programs, Circuit you Design, Games when A/D-D/A Interfacing subscribe to Peripheral Equipment NEW AUDIO DIMENSIONS

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City State Zip Code Offer Valid in U.S. and Canada Only. Canada-Add S3.00 per year Allow 6-8 weeks for delivery of first issue. Offer Valid In U.S. Funds Only. MAKING MEASUREMENTS CRYSTAL TESTER POWER SUPPLIES continued from page 115 continued from page 130 continued from page 78

Another problem when reading at a dis- good crystal is connected to the test clips. tance is the cost of long runs of ther- The output from the oscillator is then rec- mocouple wire. This is partially solved by tified by the two 1N4148 diodes and fil- splicing the thermocouple to "extension tered by Cl, a .131-µF capacitor. The REGULATED wire", less expensive thermocouple wire positive voltage developed across the DC specified over a narrower temperature capacitor is applied to the base of Q2, range. The savings are particularly impor- another 2N3563, causing it to conduct. tant when using platinum thermocouples, When that happens, current flows since the extension wires are made from through LEDI, causing it to glow. Since nonprecious metals. only a good crystal will oscillate, a glow - The low sensitivity of thermocouples requires good first -stage stability in the L FIG. 10-AN OVERVOLTAGE crowbar circuit can readout circuitry. For precision measure- e St éI be used to protect the power supply and the load ments, low -drift amplifiers or chopper - LEDI 9V in the event that an excessively high voltage is stabilized inputs must be used. (Chopper applied to the load. stabilization improves the DC drift of an is positive. That amplifier.) output from the op -amp to the gate of Thermocouples are linear enough that positive voltage is applied it on. When on, the SCR no linearization is needed for moderate the SCR, turning accuracy over moderate temperature acts like a short circuit across RI , protecting and the supply. ranges. Nonlinearity above 0°C is gener- both the load to the inverting and ally 1% to 5%, depending on the ther- If the connections to the op in Fig. mocouple and the temperature range. non -inverting inputs -amp 2Ñ9563 an Thermocouple applications are almost 10 were interchanged, we would have OR The load limitless. The wires are available in large TEST CLIPS 6E61 undervoltage protection circuit. supply would be shorted by or small gauges, in cables using a wide and regulated FIG. 1 when voltage across R, drops variety of insulations and in ceramic in- the SCR the R -E sulating tubes for very high temperature ing LED indicates that the crystal is in- below a specific level. use. The sensing junction. formed by deed OK. The circuit is powered by a welding the two wires together, may be standard nine -volt transistor -radio battery put into enclosures such as those shown n and the SPST pushbutton power switch is Fig. 11. The junction may be welded. ep- included to prolong battery life. oxied or glued directly to a surface or may The circuit is easy to build, with size- be exposed directly to air or liquid for fast for easy portability-the only real con- 'f40\C response. The temperature of molten sideration. While just about any construc- the USO steel, for example. is measured by plung- tion technique will work well, it's easiest helping the ing the two wires directly into the steel. to use a small piece of perforated con- whole family struction -board. Integrated Circuits To use the crystal tester, simply con- Well, it does ... the whole service family ... Integrated -circuit temperature sensors nect a crystal to the test leads and close the As USO's 40,000 volunteers like to say, are fairly new and are not at all standard- SPST pushbutton power -switch. If the "We're a family affair." Information, classes, at five device fam- is will glow brightly. tours, crisis intervention and more help ized. At this time least crystal OK, the LED families during the good times and the bad ilies exist. each unique in design and If the LED does not glow, or just glows times. Why? "Because life's toughest bat- output. They generally make use of the dimly, the crystal is bad and should not be tles aren't always fought in the field." fact that the voltage drop across a forward - used. Support USO through the United Way. biased diode or transistor junction de- One note on the intended use for the OCFC, or local USO campaign. creases by about 2 millivolts per degree C. tester is in order here, however. This tester IC sensors are generally offered in transis- will check any crystal for oscillation. tor or IC packages: they are not yet avail- However, it will not necessarily make the able in the same variety of assemblies as crystal oscillate at the frequency that it is other sensors. supposed to; so you can't use this tester Advertisers Index Despite the lack of standardization, with a frequency counter to test for that. a' some generalizations are possible. Oper- What the circuit will do is give you a way 267 AMC Sales l ating temperatures are similar to IC's; to quickly weed out crystals that are ob- 216 AP Products Cover 4 - 55 to + 150°C (- 67 to + 302°F) or viously bad, and, after all, that is half the 217 Beckman Cover 3 some portion thereof. Accuracies gener- battle.-Jack Fernandes - CIE 15-37 ally are several degrees, requiring user 210 Daetron 20 calibration for tighter measurements. Se- - Electronic Technology Today IS 214,215 Electronic Warehouse 4 13 lected sensors as close as ± 1°C are avail- Fluke Manufacturing 3 but are at high AMERICAN - able. expensive. Stability 212 Jameco 7 is as as with most temperatures not good LUNG 211 JDR Microdevices 5 other temperature sensors. IC's are linear, - NRI 17-19 sensitive and easy to interface with read- ASSOCIATION - Tektronix Cover 2 out circuitry. But look for specifications to The Christmas Seal People - fransamerican Cable 9 11 improve in the future. R -E Space contributed by the publisher as a public service. 213 Trio Kenwood

134 Now there's a from a common 9V new breed of transistor battery. Beckman Industrial You can run in -circuit Corporation hand- diode tests and check i held DMMs tough continuity. You even enough to withstand get a one year warranty. accidental drops, The 0.25% basic do volt accu- input overloads and destructive Drop Proof racy HD meters serve you with 7 environments. Constructed of double -thick functions and 27 ranges. The HD The new HD100 and HD110 thermoplastics, the HD100 series 110 also gives you 10 AMPS ac and DMMs are drop -proof, packed with DMMs resist damage even after dc. With one simple turn of the overload protection and sealed repeated falls. All components are single selector switch, you can go against contamination. You won't heavy-duty and shock mounted. directly to the function and range find a more rugged meter than our you need. There's less chance of HDs. Contamination Proof error. The HD series meters are Also available is the electrical designed to keep working even service kit. It includes the meter of around dirt, heavy grime, water your choice, a current clamp, and oil. The special o -ring seals, deluxe test leads and a heavy-duty ultrasonically-welded display case designed to carry both meter window and sealed input jacks pro- and accessories, conveniently. tect the internal electronics of the Feature for feature you can't HD meters. The oops-proof meters find a more dependable meter with are sealed so tightly, they even prices starting at just $169 (U.S. float in water. only). To locate your nearest distribu- Accidental Overload tor, write Instrumentation Prod- ucts Division, Beckman Industrial Protection Corp. A Subsidiary of Emerson All DC voltage inputs are pro- Electric Company. 630 Puente tected up to 1500 Vdc or 1000 Vrms. Street, Brea, CA 92621 (714) Current ranges are protected to 773-8111. 2A/600V with resistance ranges protected to 600 Vdc. Transient protection extends up to 6KV for 10 microseconds. More Meter for Your Money For starters you can get 2000 hours of continuous use Beckman ndustrIaTM CIRCLE 217 ON FREE INFORMATION CARD LITTLE THINGS MEAN A LOT

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For the name of the r distributor nearest you, This coupon is worth 100/o off the call TOLL FREE (800) 321-9668. (In Ohio. call collect: (216) 354-2101). purchase price of any size ACEBOARD. e Offer expires 12/31/84.

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City - INCORPORATED 9450 Pineneedle Drive, Box 540, Dealer Name Mentor, Ohio 44060, [216) 354-2101 TWX: 810-425-2250 ACEBOARD # In Canada, call Lenbrook Electronics 1416) 477-7722 Limited 5 ACEBOARDS per coupon. Offer valid only at participating A P Products distributors. CIRCLE 216 ON FREE INFORMATION CARD